I have lost 4 birds over a 5 month period. All with the same symptoms and I just can't figure it out. I have 4 heritage breed hens, 20 buffs. I have 2 roosters of the heritage, we believe them to be Sussex. Anyway, the bird begins by having diarrhea and panting. This girl has hung on for four days, but usually they die within 2 days once the symptoms begin. She is panting, has poor balance, isn't walking much at all, has a dirty matted vent, has watery diarrhea, and has a purple thin comb. Any suggestions? I have no mites of any sort. My buffs are all healthy. Several of my heritage breeds keep a dirty vent all the time, while my buffs all look fabulous. I don't know what I am doing wrong. I feed them leftovers 2-3 times a week, they have oyster shell, they free range about 5 times a week, they have layer and grower and scratch. Free water cleaned every 3 days with a scrub brush and no chemicals. They have a very, very clean pen. Cleaned almost daily. HELP! I am going to lose another one if I don't figure this out. I live in AZ and it was hot this summer and I thought that was the problem, so I made a chicken misting system. It is not hot anymore. SO that's not it. Suggestions?? I love my birds like we all do and I do not want to continue losing them.