I have 2 hens. One is ill. It started with diarrhea but now has progressed to walking backwards in circles, not eating, weak, wings hanging down some, very lethargic. Her comb also is flaking badly. The other hen is fine. We have alot of wild birds in our backyard where the chickens are. Quail, doves and songbirds. There is also a possibility that she could have ingested ivy. Is this toxic? I have added vinegar to drinking water and plain yogurt to diet but I'm not seeing any improvement. Any ideas?