I have a Rhode island red that has stopped growing primary feathers. This has been going on now for several months. She went through her molting and lost the big primary feathers and they never grew back again. She has all of the small downy feathers but looks moth eaten. Don't see any signs of lice or mites. She doesn't scratch or act miserable. Appears to be healthy by running and eating just like the rest of the chickens. Any suggestions on how to get her to grow feathers or what could be going on with her?