some of my laying hens (rhode island red, 18 months old) have been losing their feathers by where the tail meets the back. I first thought they were molting but they have not lost anymore feathers and I read that is not the first place they lose their feathers. I have looked for mites and lice and can't see any, Can you all please look at there pics and tell what you think is going on ? the skins seems very red and inflamed