OK...just saying, I'm not sure you should be using Nystatin and Tylan at the same time. I know people have in some instances, but it's not really advisable. You might want to double check with your vet. You are very lucky to have a vet that will do that for you! Not many will, any more, although we've been lucky to have similar experiences here.
True, lots of people will just cull their birds, but it's so rewarding when you can get one better, because it's such a challenge! I think the public interest in recent years in keeping poultry as pets rather than just food animals, took the veterinary industry by surprise, and they just aren't as up on it as they might be. Poultry veterinary medicine is always a challenge, from my past experiences. They're so weirdly complex.