Bare spot on back above feathers on a couple of my Rhode Island Reds?

[Hudson]

I have 11 hens and 1 rooster and I noticed on a couple of my hens there is a bare spot on their backs above their feathers. On one of them I noticed that is bare down to her skin, not bleeding but does not look very good. Is this possibly from the rooster trying to mate or is it from pecking from the other hens? I have not noticed any of them picking on either of these two girls but I am only out there with them for a few minutes a day when feeding, watering etc. Any info would be much appreciated!!!
Thanks! Should i put anything on the bare spots?
I have added a light bulb to my coop to increase the daylight by a few extra hours a day but I noticed this problem prior to that. Could the bulb have any effect on this?

 

[topeka]

The rooster is not gentle. I noticed the same markings on some of my hens. (his favorites?)

 

[al6517]

Over agressive roosters can cause this, but it is mainly from the hens tail feathers being bent backwards during constant mating, when other hens see this spot/area some will peck at it. It is normal, and if you look close at chickens who don't run with a rooster they look perfect at the tail.

AL

 

[JestersEye]

Our big splash Orp rooster must be racist because he is very partial to his only splash hen.

I really don't know if he's attracted to her coloring, or her docile personality. She is very sweet compared to the others.

Her back and wings are all torn up something awful! Some of the broken feather shafts even had dried blood on them, so I sprayed them with Blu Cote to prevent pecking by the other hens.

I also bought an apron for her, but I neglected to get the kind with the shoulder protection. I think I'll have to order a new one for her. Poor girl!