Sounds like they are probably OK on your part. So do they still get access to the run while confined?
Must have been terrible to have a fire.
I wouldn't waste time vaccinating for cocci, it's in every single chicken poo and only an issue when allowed to grow out of control, usually in warm humid conditions like that of a brooder. If you happen to feed medicated feed it renders the vaccine useless. But just making sure your brooder is dry is good enough... unless it makes you feel better. If you have the choice for Marek's it might not be a bad idea.
If you need to you might get her a saddle apron. Or the bully some pinless peepers to take her down a notch.
If you saw it happen suddenly, than it probably isn't parasite. But you could ask the previous owner what they mean by "covered".
Yep, I've lost two chicks to predators already this season.
And considering the possibility of confinement.
If you do add treats, maybe make sure they are good protein ones since those are mostly dual purpose ladies. They will do best with about 18%. If you wan't to feed your whole flock the same, I like the purina flock raiser with 20% protein and oyster shell on the side for layers.
If she isn't red they shouldn't peck at her, Other than blu Kote... I don't know if you could use blue food die to cover up any injury or not.
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.
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!
to have you join the family. Enjoy your time here at BYC! 
