No feathers

[forestbranch]

I am hoping some one can help, I have a hen that the rooster had destroyed the feathers on her back, now she seems to not be able to grow any pen feathers or so.
Her back is really red in part and I would like to know what I could do. I wonder if she could get a cancer.
I put some sun screen on it and hope some one can tell me what to do.

I got rid of the rooster as he was also starting it to another hen.

Thanks very much,, forestbranch