Hello, I have 12 chickens in an 8X8 coop. 6 Barred Rocks and 6 Rhode Island Reds. They are about 14 months old. One of my Rhode Island Reds has been hiding behind the waterer for 3 days, she seems to be losing the feathers on the back of her head, and the skin looks irritated. She won't come out to freerange with the other chickens. I know she is drinking, but not sure about eating. As far as I know she has not been injured. Any advise?