Chicken segregation

I have had chickens since my daughter's kindergarten teacher convinced us to take two of the chicks the class hatched.  My daughter is now 23.  
Along the way I have introduced many new chicks.I usually keep about a dozen chickens.  During the pandemic I was down to 5 hens and a rooster.  I couldn't get chickens locally like I had always done. I ended up ordering them. I had to order 15 minimum.  At this point I have 4 older hens 4 or 5 years old (it's hard to remember). 14 of the mail order hen's 2years old in September.  So I got 8 chicks this spring.  I did everything like I always do. Start chicks in a bin in the house, once they are fully feathered and can handle the outside temperature I put them in the coop where the can see the other hens, but are protected in a safe part of the coop. After a while I will open it up, and if it seems ok leave them to it.  My new hens are maybe 3/4 adult size. 4 months old. No one seem to be bullied, no missing feathers, or wounds. But the young always seem to be together in a different place then the other hens.  The young roost in the chick part of the coop, instead of the roosting bars in the main part of the coop.  At least when I'm around there is no interaction between older and younger.  The only one mingling is the the rooster ( unfortunately one of my she's is a he).  Is this a problem?  I don't know?  It's strange, always before the new hens would become a part of the flock.  This feels like 2 flocks.
I enjoy variety so my older girls are an Easter egger, a Rhode Island Reds, and two Salmon faverolle.  My mail order girls are 5 Sapphire gems, 4 Issa Browns, and 4 color eggers (not sure what they are because the hatchery wouldn't tell me). My new chicks are 2 Rhode Island Reds (1hen, 1 rooster). 2 Olive Egger I worried one of these may be a rooster because it is sleeker, doesn't look like the other?  I'm just not sure like I am with the red who is beautifully obviously a rooster, and 4 blue Marans.  So it's not a being different thing, they are all different.
I just haven't seen this before.  Have you?  Should I do something?  I tend to be let nature take it's course, unless harm is involved.    Thanks

I have had that happen.  I introduced 4 or 5 new chickens and they stayed to themselves for quite a while.  Eventually they all joined together, but it was quite a while, months for sure but I can't remember exactly.

I think this is normal - at least, it always happens in my flock if I introduce a large number of chicks (6+) at a time. Eventually they completely integrate.