Your State Department of Animal & Ag should do necropsys. Ours charges $30 for up to 3 birds. If your birds are pets and you don't plan on selling them etc.... you can treat them. They do have a vaccine for it. Treatment for Corzoa.... 1 teaspoon of Gallimycin powder & 1 teaspoon of...
You can buy Baytril liquid from allbirdproducts.com for $25 for 25 mil w/o an RX for pet birds. My vet says to put it in the syringe that comes with it and put it in the mouth instead of adding it to the water.