I'm so sorry about the baby Sun...That's exactly why I mention that he had to be kept in a Brooder at the correct ambient temperature, and his hand-feeding formula had to be between 104-110 degrees F at all times, because most baby parrots at that age do in-fact die of a Crop infection due to their breeder not caring about either temperature...I'm not saying that you weren't using a cooking-thermometer in his formula or weren't keeping him in a Brooder, it very well could have been the "breeder", and I'll use that term loosely, because anyone who would sell someone an unweaned baby parrot/bird isn't much of a breeder at all, they're a Broker...So I wouldn't be surprised if the breeder wasn't even keeping them in a Brooder or measuring the formula temperature...
I too would get your new bird to a Certified Avian Vet or an Avian Specialist Vet for a complete Wellness-Exam that must include full Fecal-testing on a fresh sample you bring-in with you that day, and then also full, routine, baseline Blood-Work, along with requesting that they do each individual Blood-Test as well as the routine, baseline Blood-Work they always do...Each one of those Avian Viral Diseases is a separate Blood-Test that they will just add to the Blood-Work order, and must be done because you need to know if he is sick or is going to get sick, or if he needs to start treatment with an Antibiotic or Anti-Fungal for any infections. The breeder you got him from is not one I would trust, so unless they gave you a Certificate of Health stating that he's tested-negative for each individual Avian Viral Disease, has no active Bacterial or Fungal Infections, etc., then you must get him completely checked-out ASAP...
***Just in-case you're not aware of this, all birds/parrots hide any and all outward signs or symptoms of being sick or in pain for as long as they possibly can, and they do it very, very well...It's an innate, natural survival-instinct that they all possess, and that keeps both them and their entire Flocks from becoming "easy targets" by predators, because if a Flock of birds/parrots has a sick or injured looking or acting bird in it, that makes the entire Flock a target...So because of this natural instinct that all of our pet birds/parrots possess from the time they hatch, by the time we as people/their owners first-notice that are birds are acting like they are sick, in pain, or simply that something is wrong, THEY HAVE USUALLY ALREADY BEEN SICK FOR AT LEAST MONTHS, IF NOT LONGER! Often it's too late to help our birds by the time we realize they are sick, even if we take them to a Certified Avian Specialist the same day we notice that something is wrong, it's often too late...And they often die from very common, easy-to-treat Bacterial and Fungal infections because off this...It makes for a bunch of hyper-paranoid, neurotic parrot-owners, especially life-long ones! (Myself included!)
***So this is why getting your new bird to ONLY a Certified Avian Vet or Avian Specialist Vet is very important, it should be done with every pet bird/parrot at least once a year anyway and should include a full Fecal Testing an full routine, baseline Blood-Work...And some people also get an X-ray done during their yearly Wellness-Exams (I do this because you can see the entire bird's body on one X-ray, and this is the best way to catch things like growths/masses/tumors extremely early while there is still something you can do about it, and it also lets you see the size of their liver, their kidneys, their heart, and their pancreas, the 4 organs that become diseased the most in pet/captive birds, usually starting when they are very young, usually due to diet, a lack of exercise, and environmental contaminents and dangers around them)...
***Just make sure that you NEVER allow any Vet to put your bird under ANY sedation and/or anesthesia AT ALL just to do a simple blood-draw from their neck!!! This is a sure sign of a Vet who is not an Avian Specialist Vet, certainly isn't a CAV, has little to no experience treating birds/parrots, and is very uncomfortable treating them! Most "Exotics" Vets in the US will tell you that "they have to use sedation or anesthesia to take blood from a bird's neck", but it's just not true, it's totally unnecessary, it's a risk that doesn't at all need to be taken, and even more importantly it's a sign that the Vet you're talking to/seeing is not at all qualified to diagnose or treat your bird...There are some "Exotics" Vets in the US who are also Certified Avian Vets, but they are very rare, so the best way to find one is to use the search-tool here in the forum, I'll try to find the link to it and post it here again, or someone else may have it ready to post...There are more Avian Specialist Vets in the US and IN ALL STATES than people usually think, they often say there is no CAV or Avian Specialist in their entire State, or there are only a hand-full, then they use the search-tool here and find dozens... (a "Certified" Avian Vet or an Avian Specialist Vet does not at all mean that the Vet "is a member of the Association of Avian Vets, that means absolutely nothing other than they filled out a form to join, sent them a check, and got a certificate or placque back in the mail to hang on the wall, and that they get a quarterly newsletter from those associations, that's all it means in the US)...