@Macawnutz, thank you for the valuable information! It's good to know that those medications are effective for treating bacterial/fungal infections - I couldn't find much info on them so I was thinking they might be outdated or not very strong. It actually wasn't my vet who suggested aspergillosis. It was me being neurotic the other night, looking up any possible causes for his symptoms because he's not improving. At the beginning, the vets were going to keep him for a few more days, give him a few more vitamin injections, but I brought him home because I had a bad first impression and I didn't really trust that they would be gentle with him (they DID treat him very well, for the record!!!).
I'm going to ask them tomorrow if they actually thought there was possibility of an infection or if they just prescribed the meds because I was so adamant there was no way it could be a VA deficiency...
I will definitely have the proper blood test to see if he has the deficiency. Hopefully a regular vet close to me who sees birds would be able to do at least the blood test, it would make things a lot easier if I could first rule that out, and then do all the other stuff at the other avian vet.
I am going to feel like an absolute idiot if it turns out that it WAS a Vitamin A deficiency all this time.... I mean if those antibiotics/antifungals are so effective, you'd think he'd have shown improvement by now. It just doesn't make sense to me how he could have had VA deficiency. Vitamin D maybe, because he wasn't getting sunlight. I've heard that D and A work together so it's possible that the lack of D contributed to A not being absorbed? I don't know, just speculating at this point.
Main point is, THANK YOU for your help. You have all been amazing. I was so stressed out this weekend but I feel so much more optimistic now