My RIR has a very red, swollen butt. She has plucked all of the feathers away from that area, and when our 2 roosters try to mount her, she runs away, something that is not normal for her. I think her hiney is sore. What could be causing this? I don't know if this is important, but several weeks ago, she had a large mass of poop feathers stuck to her butt. We cut it off but left some feathers. She plucked whatever we left.