There is no sign of attack/invasion in the coop. Her rear-side is absent of feathers and has a sizable wound reacher back to her butt, which is also bleeding. No blood in stools, however. Have separated her from the other 4. Not sure what is going on?! She is walking, eating and drinking. Is this henpecking? The bloody butt is the only thing that make me think not. Other chickens appear totally fine.