I have three hens, all ten months of age kept together in an enclosed run with coop attached. One of the hens, my RIR has lost some feathers, in a horse shoe shape above her tail. All her tail feathers are in tact, fluffy bloomers intact, laying like a champ, and looks great overall. Good appetite, normal poop, not stressed or picked on (she is the top ranking chicken, in fact) The feather loss seems to be underneath her main feathers, you have to kind of gently push her tail feathers to the side or lift the lower back feathers to see it well. It is pretty much bald in a 1.5 inch strip, and RED skin, although not scabby oozing or broken at all. A couple of feathers are starting to sprout back out there as of today. I noticed this a week or so ago. No mites or lice that I can see. They get layer crumbles, free range lots of green weeds and bugs, treats of sunflower seeds, leftovers, flaxseed, etc. Can anyone help??