We have four chickens, but we seem to have a problem with the leader. She has a really red bottom, this doesn't seem to aggravate her she also doesn't scratch it. It started with just a bit less feathers, the problem got worse so we got some insect powder and followed the instructions. We left it for a bit to see if it would help, but the problem just got worse.It looks really bad but when you touch it she doesn't seem to worry about it. What could be the problem?