This is what I was afraid I might hear.
As it turns out, despite being called an "Animal and Bird Hospital", the vet Quinn was seen by turned out to not be an avian vet. Seems we don't have any near here.
I'm calling around now to see if I can find a clinic that at least can do proper tests to determine what is going on (they weren't suggested last time).
Is AGY treatable at least? Can birds have it for some time before it causes these kinds of problems? What causes it?
I don't know why I'm having such terrible luck... I've been keeping Parker's cage very clean, giving her all the right foods, washing my hands before I do anything in her cage. Everything was good up until today. I opened the garbage bag to look at yesterdays cage papers, and they look normal, minus one possible seed in one dropping.