This morning I noticed the other chickens beating up on one of my hens. They all ran off to peck at some grass clippings and she was just standing there, kind of dazed. I took her out of the pen and turned her loose in the yard. Slowly, she started coming around and was really thirsty when I gave her some water. Then, I noticed a big blob of white, crusty poop stuck to her butt feathers. What's wrong with my poor chicken?