Welcome to BYC.
Chickens hate change and they usually take a while to flock together with newbies no matter how carefully the integration is done.
Especially if the new birds are a different age group from the existing birds since layers don't hang out with the pullets even when the pullets are raised in the flock.
Having pullets starting to lay right now, I'm seeing the girls who have started laying moving into the group with the layers and leaving their hatchmates behind.
If the newbies aren't being beaten up or driven away from food and water then just give them time and the flock will get together eventually.