Since the fall two of our 7 hens have had feather issues (or lack of). Silver Laced Wyandotte has a bare spot on the base of her back (see pic) and the Americanus has a bare bottom and only downy feathers on her lower back. I have checked for insects/lice...no sign of them but treated anyway on the bird and in the coop/run. We spray them with bluekote just to keep the area covered. None of the other hens are pecking at them, anymore. They primarily eat extra egg layer pellets and get meal worms and greens as treats. Any suggestions to point us in the right direction to heal/promote feather growth would be appreciated!