They could be adjusting the pecking order, due to the new location and figuring out who the top bird is, now that they were removed from the established flock. The problem is this kind of thing seems to develop into a habit and can get very nasty. If they are working out pecking order issues (and already know each other) mine usually just go for neck feathers and there is a lot of reaction from the picked on bird. If it is more feather picking going on I see it at the tail and vent area, and the bird being pecked is snuck up on, especially when foraging or eating with their head down. This is what seems to develop into a serious habit. Pecking order stuff stops for the most part once everyone knows their place.
I don't have a ton of experience with feather picking, they sell some anti pick liquids that help. I have used vapo- rub and blu kote, they worked well for slight issues I had. The blue kote covers tempting bald areas on the bird and seems to deter picking. The vapor rub they hate the taste but it's very messy. I used it when I had removed & then put back a bird upsetting the peck order. They were pulling out her neck feathers and bloodied her comb. The vapo- rub stopped them from injuring her any further and it works well on the comb. Once the main bully got a taste of the vapor rub she left the other hen alone! Confinement seems to make picking worse so give the birds more space/ time to free range & something to do when they are cooped up.
If you think it is feather picking it could be made worse now that the picker only has 2 other hens to pick at rather than a flock. Also there could have been a roo or more dominant hen who prevented this in the larger flock. I have seen Roos do a great job of putting a stop to this and keeping the peace.
Good luck and have fun with the new birds.