Okay.. a lot of students and the resident experts (CAV) @ the University have thought and talked about this.
They cannot give you a diagnosis, because they have not seen Jaquo in person.
(though they wanted to if they could, they all wish Jaquo the very best and are touched you care so much about your parrot! )
Here we go:
tylan = (another) antibiotics
they will not give advice about the use and dosage because they have not seen the bird...but......
if your bird is having reporatory problems- (and previous antibiotics did not help) it could (probably) be because of a fungus infection and not bacteria.
(apergillus / aspergillosis is a realy hard to fight, sometimes it returns)
Antibiotics like tylan will *not* help against fungus.
You need an anti-fungal medicine like turbilicine form your vet.
recap:
Turbiciline fights fungus (and aspergillosis)
Tylan/Tylosin fights bacteria
Antibiotics (Tylan) will upset the intestines (smelly poop etc.) so use a probiotica for parrots to help the the intestines.
(if you really, really cannot find any for parrots -> let me know!)
example: It is this stuf:
probiotica voor vogels - Hareco - dier en vriend - Papegaaien en Dierenspeciaalzaak
(a lot of online shops have it, and will send it to you)
We could not read the bottle (I guess it says Tylosin?), sorry (cyrillic is hard if you are not used to it / you are very clever you can do both!).
They are very sorry to hear your vets are in disagreement with each other and you and your bird are not helped very well.
Don't give up!!
===
so thats it from the university - for now-
if you have more questions, they will be happy to try and help you.