I have two Isa Brown hens both 20 months old, Sugar and Spice. They are inseparable and both good layers. Sugar has her white under-feathers exposed on the front edges of both her wings. See photos. It appears some of her feathers there had broken off. She has been looking like this for a couple of months now. The other hen, Spice is normal and has no white feathers exposed. I have not seen any mites but I treated both hens for mites twice just to be on the safe side. Both hens are acting normal and neither seems to be stressed. They sleep together, roosting in an enclosed hut. In the morning they are released into a screened in pen for about an hour. After that they are released and free range together in my back yard all day. Any ideas what is going on with Sugar?