What colour are they,the only reason I ask is when and however any of us integrate hens,did you know that they do actually notice different colours.
i.e. I have white hens in my main flock,I also have some white Capons for Christmas,The wind here took the fence panel down the other day,I arrived home and thought,oh no,there is going to be bedlam going on,and nothing,not a bicker or any unfriendliness at all,it is true.Now if you were to add a white hen to an all brown flock-there would be problems!
I have always had mixed colour flocks,so if I had to integrate any together,it would be pain free,there shall always be a little pecking going on in the coop at night,it is just their way,but they soon settle down.
I also had a Mum whom became aggressive towards one of her chicks,I thought she was going to kill her actually and I had to tell mummy off,the chick she picked on was a different colour to the rest,my way of dealing with this was to put Mum back with the chicks for a little while longer,I know it may sound odd,but I wonder if the mother is actually picking on her because she has come into the main coop-and may get hurt?! ??