My little chickens are like their own flock, but I have older chickens 3 1/2 to 6 1/2 months old. The little ones are about 2 months. They were pecking at the little ones last night and I don't think they knew what was going on. I wasn't sure if its pecking order or they just hate them. Here is one of the little ones. We think she is a silkie. Here is one of the middle aged ones. She is a golden buff. Here is one of the older ones. She is a white leghorn.
With that age difference the little ones are going to get picked on a lot, possibly killed if an older hen is determined enough. If there's no blood and the littles have plenty of space and places to hide, you can just see how things go. If not, pull the littles out until they're closer in size to the big girls and try it again.