Welcome to BYC. I think she may be having her feathers picked by one (or more) of the others because of the redness on her skin. She also could be molting if she didn't molt in the fall, but you should see feathers in the coop. Check her closely for mites or lice on the skin, and treat with 5% Sevin dust if you see any. Feather-picking can become a habit. I would watch for the picker, make sure everyone has at least 16% protein, and you can increase this with scrambled egg, low salt tun, dry cat food, or give a 20% all flock feed with crushed oyster shell on the side. Make sure they have enough room and some things to climb on or activities to keep them from becoming bored. Letting them fee range can help.