My older girl, she's about 6, has bright red patches on the points of her keel bones. She has not been laying for some time now, at least a year. She is the boss chicken, so she takes no nonsense from any of the other chickens. I have spotted her picking at either side as if it's itchy. No surprise! Here is a photo of one side of it to demonstrate what it looks like. There is one bald, red patch on either side. She has also had poopy butt feathers for some time, but she seems otherwise in good weight. My flock has mycoplasma and I did have to treat her last year for it. I put some ivermectin pour-on on her skin yesterday, 4 drops with a 22g needle. (of the 1 mL for 22 lb strength for cattle). I see no indication of lice or mites on her or anyone else in the coop. If she gets better from the ivermectin, I'll treat the rest of the chickens. If you have any other ideas, I'd be grateful!