Out of 9 birds I have 3 RIR about 29 weeks old. They are constantly being picked on by the others. One is laying and one is a complete outcast. She sleeps alone, eats when no one is around and follows the flock at a distance. The other RIR is fast and thin and sleek looking. She can mingle if there are other diversions to keep the others busy. So I caught the thin one yesterday and as I was helping her preen her feathers I noticed that they were matted down in areas behind the wing, under the wing and down her side. Not much on the belly area. Let me know if I should be worried and / or tell me what this is. The matting does not pull off the feathers without pulling the feathers out.