I'm glad you found a great Avian Vet with experience who knows what they're doing; some of us, including myself, have taken our Avian Specialists, Reptile Specialists, etc. for granted because we didn't realize how difficult it is to find a good, educated, experienced Specialist Vet...So that's awesome...HOWEVER, I'm very surprised that an Avian Vet who took a culture and diagnosed him with an active GI Yeast-infection would not also put him on a round of prescription Anti-Fungal medication, because no Probiotics or diet-change is going to treat/cure/get rid of the Yeast-infection he already has!!! These are only "Preventative-measures" to keep this from happening again, not treatments to cure/get rid of a GI Yeast-infection he already has...And it will only continue to get worse without treatment.
***I highly advise you to keep giving your Amazon and ALL of your birds a daily Avian Probiotic from now on, not just when they develop a Fungal-infection!...Probiotics not only keep the amount of beneficial-Bacteria throughout their GI Tracts at high numbers, which keeps Yeast and other Fungi from growing (from the Crop all the way through to the Cloaca), but Probiotics also help them to better digest their food, absorb nutrition from the food, and keep the lining of their stomachs and intestinal-tract from becoming irritated or upset. Of course the big deal is to prevent them from developing GI Fungal/Yeast Infections like your Amazon now has...***I'm kind of surprised that your Avian Vet didn't put your Amazon on a course/round of prescription Anti-Fungal medication since he found that he has an active Fungal-Infection; Probiotics DO NOT treat or get rid of the Yeast/Fungi that has already grown inside of their GI Tracts, they only encourage the growth of beneficial-Bacteria throughout the GI Tract...So typically once an Avian Vet, Reptile Vet, etc. finds that their patient already has an active Yeast/Fungal Infection they will put them on a single-round/course of an oral Anti-Fungal medication, and then they also typically recommend that they also take a Probiotic daily, so that once the Anti-Fungal medication kills-off the Yeast/Fungi that is causing the infection, the Probiotics can replenish the beneficial-bacteria that protects the GI Tract from Yeast/Fungi growing again....However, once again, giving your bird a daily Avian Probiotic WILL NOT get rid of the Yeast/Fungi that's already grown and is living in his GI Tract and causing the infection (nor will a diet change)...So both the daily Avian Probiotic and the diet change are simply "Preventative Measures" that will help to keep your bird from getting ANOTHER Yeast/Fungal Infection IN THE FUTURE and that's it.
***Make sure that you are watching not only Bonker's poop every single day for irregularities from this point forward, specifically that horrible smell that you will now remember forever, lol, and also for any bubbles in his poop, as they are a sure sign that Yeast is fermenting in your bird's poop. The color-changes of their poop are also a symptom of a possible GI Infection of some kind, but the problem is that there are a million things that cause their poop to change colors back and forth and back and forth, and the majority of them are not harmful things causing the color-changes, but typically very benign things like something that they've eaten...So the most-reliable, "Direct" sings/symptoms of a GI Yeast/Fungal Infection in a bird are #1 Bubbles in their droppings (caused by Yeast fermentation), #2 An extremely foul smell that is usually described as being a "sour" smell, #3 A foul smell that is also "sour" smelling coming from your bird's mouth/beak/breath (a lot of GI Yeast/Fungal Infections start in their Crops, and if this is the case you can easily smell a sour smell coming from your bird's mouth/beak)...And of course you also need to watch Bonkers carefully for any "general" signs/symptoms of a bird being sick, including Being More Lethargic than usual/Sleeping more than usual, eating less food than they do normally, stopping eating all-together, any vomiting at all (not "regurgitating", which is hormonal), the bird being "fluffed-up" more than usual or all the time (trying to stay warm due to chills caused by a fever), etc.
Just keep a very close eye on him for the next few weeks, because again, I'm very surprised that the Avian Vet did not put him on any Anti-Fungal Medication at all, such as Nystatin, after he took a culture and positively-diagnosed him with an active GI Yeast Infection...I totally agree on his recommendation of putting Bonkers on a daily dose of an Avian Probiotic to prevent "future" GI Yeast/Fungal Infections, but once again, Probiotics will not treat nor cure an active GI Yeast/Fungal Infection that your bird already has when he starts taking the Probiotic (nor will any type of diet-change)...Think of it like putting a Flea-Collar, which "Repels" Fleas, on a Dog who already has a Flea-Infestation; the Flea-Collar won't kill or get rid of the hundreds of Fleas that are already on the Dog, it will only prevent them from getting another Flea-infestation in the future. In order to get rid of the active Flea-Infestation you have to treat the Dog with a medication that will kill the Fleas and the Flea-Eggs that are already on the Dog...It's the same situation.
***So you're going to have to watch your bird very carefully for the next few weeks and regularly inspect his poop and watch him for any signs/symptoms that he's sick and doesn't feel well, because an active Yeast/Fungal-infection isn't going to just go away on it's own (usually). I'm assuming that right now the only signs/symptoms that Bonkers has had/shown are the changes in the color of his poop, as well as the horrible smell of his poop and that's it. As a GI Yeast Infection progresses the signs/symptoms are very similar to that of a stomach bug/illness in that they start to actually feel badly, they stop eating as much as they usually do, they start to become sluggish and sleep more than they usually do, they may or may not vomit after they eat, and their poop may become even more abnormal in either direction, meaning that it may become very loose, runny, and frequent (usually this is what happens), OR in some cases their poop becomes very thick and chalky (not typical, but does occasionally happen, especially if the bird stops eating and drinking as much as they normally do)...Either way, you do typically start seeing little Bubbles in their poop as the Yeast/Fungi multiplies more and more and is present in their GI Tract for a longer and longer period of time, which allows it time to ferment. And the smell of the poop typically stays pretty bad; the development of a very "sour" smell coming from their Crop, which you can usually smell if you get close to their face when they open up their beaks, usually starts once the Yeast-infection in their lower-intestines has time to spread up to their Crop. So just please keep a very close eye on him, and if his poop stays the same as it is or you start seeing any bubbles in it, or if he develops any new signs/symptoms of illness then you'll need to take him right back to the Vet ASAP so that they can put him on the appropriate Anti-Fungal medication to treat the specific Fungal Infection that he has (Yeast is Yeast, so if that's what he saw then typically they put them on a round of oral Nystatin)...And of course do give him the Probiotic that the Vet gave him every day, and as I already mentioned I would absolutely start giving ALL of your birds a daily Avian Probiotic each morning from now on, just like a daily vitamin or supplement that we take, as it cannot hurt them at all in any way, only help them and keep them healthy, and keep this from happening again, so none of them will have to go back ot the Vet for a culture and then have to take a round of prescription Anti-Fungal medication to get rid of it.
(I have been giving all of my parrots a daily dose of Qwiko Avian Probiotic Powder every morning on their Pellets or on top of the 1/4 cup of Seed-Mix they also get each day since the day I brought each of them home, so for years and years, and not one of them has ever developed ANY type of GI Infections, nor had any appetite issues)...
