One of my hens has developed a "bald" rump. The entire rump is involved, as well as some small areas on the "shoulders". It looks exactly like the pictures on the page [https://www.backyardchickens.com/forum/viewtopic.php?id=208399]. Within the patch, there are broken pin feathers, normal pin feathers and normal, but inadequately preened, mature feathers (sticking up in every which direction, barbs not smoothed out, etc.). Another hen has a bald head, with irritated-looking skin, but no broken or pin feathers. A few of the others have disheveled, but not bald, rumps. The skin in the bald area is mostly normal, but one quarter-sized area looks irritated and scabby (not a wound, and not bleeding). I haven't seen parasites on any of them, although I've checked thoroughly, including at night. I haven't seen feathers in the pen, so it isn't a molt. I haven't seen any pecking, either. Egg production is fine. I have a very (sexually) active roo. He's always been rough with the hens and has recently become aggressive towards me. All of them have been stuck in an 8x12 converted horse stall for 2 months because of several feet of snow on the ground, and a host of hungry predators hanging around the barn. I'm inclined to blame the roo. Any thoughts?