Most of the older hens didn't mind the new additions. They went about their business and just ignored the babies. But I had one Plymouth Rock that felt like she needed to let everyone know who is boss. She would chase them around and peck at them. I separated her for a couple days and now she has seemed to calm down.
I separated all of the birds for the first 3 days when I introduced the babies. During the day I would put the little birds in the big run and move the older birds to the tractor. They were able to see each other but not have contact. At night I would put them all together in the house. This seemed to work well. Now I have them all together full time.
The little birds are still a bit shy. They pretty much stay in the house most of the day. They did sneak outside once and peck at the ground for a bit. Right now they are like 2 high school cliques! The 7 veterans and the 4 newbies. Hopefully once they get a little older they will all mingle happily.