Baytril almost always causes a secondary yeast infection. So talk to your doctor and explain the bubble stool and ask to have nystsin added. It a cheap safe treatment fir yeast. Vets should be well aware of the risks of yeast when on baytril .
Azithormycin is also a broad spectrum antibiotic that's works excellent in birds and only a small dose every other day s needed with only a 5 dose treatment needed. Vet can call into human pharmacy. It saved my quakers life. But some vets are less familiar with it. My avian veterinarian is a global consulting veterinarian ( to other veterinarians ) and she is working hard to educate the community. Its delicate to discuss wanting to change how your burds being treated..and I know I'm just a girl on the forum. And I'm not a vet, but I ve done a lot of work with sick birds ...there can be reasons why certain medications are chosen, by tge actual veterinarian who has seen your bird. But you can always mention that you have a friend who's bird was very very sick and Penny quaker was. And yiu found out your friend was given azithormycin and how well hers recovered. And would thst antibiotic be something that might work fir yours?
Its difficult to know what's best... and I have zero way of truly knowing what's best fir you and yours. I'm not sure what an older burd not exposed to other burds picked up, and if there is something else going in that lowered her immunity. Sometimes nasty bacteria can be on greens and veggies and fruits. Or coliform count can spike in tap water ..or other ways to get bacteria. But if they are just trying to choose a broad spectrum antibiotic ( which bsytril is) I personally really stand behind azithormycin