Back and Tail feathers...will they ever grow back?

[Chickerdoodle13]

I got a flock of ameraucanas from a lady last summer. They had been with two or three roosters (can't remember how many came with them. They were rehomed). At the time, many of the hens' backs had been really shredded and were completely bare. I figured the feathers would grow back in. The only rooster I had for the longest time was a little bantam mix, so I knew he couldn't do much damage and he was always very gentle with the hens.

Now it's been a year later and many of the hens still don't have feathers. I know it is possible for birds to have their skin so damaged that feathers never grow back, but do you think there is a chance they will ever come back? It seems like they still have the little shafts under the skin. These hens are about five years old now.

 

[Chickerdoodle13]

Also, I should just add that I did have a RIR roo in with them, but my chickens and the ones I got from her who did have feathers were fine, so I'm pretty sure he was not over-mating. I got rid of him recently and picked up two very young cochin cockerals. I'm not sure I will be keeping both, but I do have chicken saddles if they are needed for those few. Right now though, the cockerals are too young to mate.