It could be the reason for feather loss, but would still look like mating damage. Palm size is pretty big, and doesn't seem to me like it could happen from just ONE incident. 
). They are just over 1 year old. I rescued them from a house in my town that had a fire. The owners had to move and the new house didn't have a coop ready. I have not treated them for anything because the previous owners said the hens were covered. I am feeding them Purina Layena and minimal treats (half a grape each today, a little bit of greens yesterday). They are in a 40sq foot run and a (about) 12sq foot coop.They are confined for now because there has been a hawk nearby and our neighbors lost a chicken to it recently. I am hoping to let them free range soon. The chicks will be ordered from a hatchery that vaccinates against cocci but I'm not sure about Marek's.
So glad you joined us. Thanks for being such a good Samaritan and rescuing those birds. 
It's a good introduction for you to what's coming when you get your chicks. Sounds to me what you're describing as feather loss due to mounting. There's a wealth of info, knowledge and experience shared in the multitude of threads. Browse around and see what interesting stuff you can find. By all means post away when the desire strikes you, especially if you have questions (provide as much detail/info as possible and pictures truly help)... With all the great folks here, generally someone will respond in no time at all. Please make yourself at home!
If you saw it happen suddenly, than it probably isn't parasite. But you could ask the previous owner what they mean by "covered".
And considering the possibility of confinement.
Happy
to have you join the family. Enjoy your time here at BYC! 
