rotting mouth - Page 2
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The inside of the mouth looks like it could be canker, but I would also wonder if there isn't a tumor or infection under her beak. Fowl cholera, Mareks disease, and coryza can cause a swollen wattles or neck. I think a vet might be your next step. You could also cull the chicken and send the refrigerated body in to your state vet for a necropsy. Here is a link for contact info: http://www.usaha.org/Portals/6/StateAnimalHealthOfficials.pdf
I have a pigeon that I'm treating for canker right now. Here are two link that might help you:
That swollen wattle is probably full of the same stuff you see in her mouth. If she were mine, I would try lancing it and I'd start her on antibiotics. The wattle will bleed a lot, so you should probably have styptic powder for that.