Hello!
I would really check them all over for mites and lice, just to be safe. I'll bet you're right and they were probably overcrowded in their previous home.
I like a product called Blue Cote. It looks really bright blue, but it heals the wound, and also the blue color isn't attractive to hens, so the others won't peck at the bald spot. It comes in a spray, or a bottle. Unfortunately, it'll look like your ink pen exploded on the back of your hen
But it works very well.
As far as the rough behavior, anytime a chicken gets a new environment to live in, the flock will establish it's pecking order, and that is probably what's going on now. It'll probably be rough for the first week, but soon, things will settle down nicely.
I would just quietly observe, in case you have some really, super mean hens, but you do have to give them a bit of time to work that pecking order out.
Good luck with them! I'll bet they're so happy to be somewhere new with better care and more space!
Sharon