Ok so I would say that I am new to chickens but have caught on pretty well, however I have never introduced new pullets to the 4 I started my flock with. This is about to change. I got two leghorns when they were 6 weeks and they have been in a smaller coop and run that ran along the big run so they have been in view of the big girls this whole time. They are now 11 weeks how would be the best to move them in, if I even can. I need the small coop for some chicks I have had in the house.
Sounds like you have had the new chicks separated for a few weeks now. If you free range at all, I would let all of them out together and see how they do. There is going to be some pecking and chasing, but as I can tell you from my experience this is normal, and they will work it out. As long as there is no blood just let it go and keep them all together. Let us know how it goes.