When certain hens in my flock get a bald &/or red spot on their back, I assume it's from the Rooster standing/grabbing on their back & breeding them often. If it gets red, feathers plucked, or bleeding I apply a No Pick solution (it's red & has a fragrant smell) from the feed store that deters the other hens from plucking out quills, pecking & also helps the hens skin heal. A couple of my hens were getting over plucked by other hens & I found some chicken aprons online that worked well as long as the apron was left on long enough for their feathers to come out of the quills all the way, leaving no tell tale signs that it had ever happened.
My flock always has a big plastic tray available for dust bathing for mite control: wood ash, sand & a little DE; they just love it. Best wishes.