Rooster Troubles- Hens in the flock suffering injuries. *pictures*

Ok, so, we keep backyard chickens mainly for fun, and for eggs. We started with a very small flock, five hens and a rooster, and we started having problems. The roosters were breeding the hens ALL the time, and they started to tear up the girl's backs after a while. Eventually, we lowered our rooster population to 0 to give the girls a break. Well, 6 months later, they still haven't healed up or regained feathering on their backs. One of the girls actually looks sunburned on her back, though she isn't peeling or anything and doesn't appear to be in pain. These five hens always look dirty and messy compared to the others, and we're not sure what to do at this point. I posted two pictures of them below, so you can get an idea of what we're looking at.

Any help would be appreciated, as I can't find anything that adressess my problem online.

This is probably the best looking of the five.....
And this would be the worst, the one I'm worried about sunburn on. There is no way that is her proper skin color. I feel bad looking at it, though she doesn't seem to be in any pain.

Thanks in advance for any answers.
~Ruby