I'm new here and new to having chickens....about 5 months. I have a large enclosed coop with a dirt floor. I have 18 hens and 2 roosters. I go collect my eggs each night after work. Last night one of my Plymouth barred rock hens (I have 4) was bleeding from her comb and "hiding" in one of the nesting boxes. I collected my eggs and fed and changed the water. While I was doing this, she came out of the nesting box and the rooster attacked her and jumped on her back and began pecking her head. I swatted him away and grabbed her up and cleaned her up and held her. I notice that all of her feathers on her head were gone. I'm wondering why Rooster Cogburn is picking on her? They have all gotten along ever since I got them several months ago and RC didn't attack any of the other hens, just this one. Any ideas? And should I isolate her until her feathers grow back on her head? I checked on her this morning and she was back in the nesting box (not broody) and seemed ok.