This is normal. They need time to establish a new pecking order and it involves a little violence. You can try putting the new birds in a large wire dog crate or some other pin that allows the birds to see each other and be "together" without being together for a few days at first to get to know each other. This may help a little but it will not make them instant friends.
Keep a watchful eye and intervene if you see blood. Remove the injured chicken and wait for her to fully heal before putting her back with the others. Also watch to make sure the older birds are getting to eat. If a bully is guarding the food add a second temporary feeder until their issues are resolved.
Unfortunately this is their natural social behavior - but they should work it out on their own.
Look around make make sure you have enough space in the coop, nests and roosts. Overcrowding makes bully way worse.
