That is perfectly normal. Until those chicks reach maturity, usually around when pullets start to lay, the older hens are likely to peck them if they invade personal space. It is the pecking order, older hens often can be kind of vicious when their personal space is invaded by a subordinate, especially a chick. Normally as long as the chicks don't get too close they don't bother them. Having enough room to avoid the older hens is important when you have chicks. Usually the chicks learn pretty quickly to stay away as long as they have room. They are usually the last to go in the coop at night and sometimes they don't want to go in at all.
So what can you do? I don't know how much room you actually have in that coop, hopefully enough. As long as he chicks are not being injured you can keep doing what you are doing as long as they sleep somewhere safe from predators. Once they mature they will join the older birds. You usually need more room for integration than for a flock when they are all mature.
If the chicks start to get injured you might want to move them to the old coop until they mature. Or maybe build a pretty predator proof run around the new coop so you don't have to leave them locked in that new coop for a long time.
Cassowaries as ornamental birds
Golden duckwing genetics
I culled my first cockerel, now what?
*Answer These Questions The Best You Can Please *
