Also look for a source of poison's they could have gotten into. Including fertilizer and weed killers on your lawn. Also check you feed. Does it smell normal? does it look bright and like it usually does? I once got a bag of feed that had black mold near the bottom. Aflatoxin killed a lot of young birds and my dog because she liked to eat spilled feed.
Without seeing them in person, it doesn't sound disease related, that does not mean it can't be. But it sounds more like botulism / poisoning / venom related. Also check for mites.
Without seeing them in person, it doesn't sound disease related, that does not mean it can't be. But it sounds more like botulism / poisoning / venom related. Also check for mites.