So, who was laying before? And how old are the older bantams? Are the cockerels/roosters mating the hens or ganging up on them? If so, they might be stressed, so keeping them separate was a good choice if that was the situation.
How big is the coop, and how big is the run? We have a 50x10 run, part of which is under the coop (that coop is elevated 2.5 feet above the ground with an access deck), so they have a variety of places to be, enough room to get away from each other and multiple points of access to food and water.
However, one rooster (of 2) did not like a breed of hen that we had and chased and pestered them always. They were eating and drinking, due to multiple locations. They are 38 weeks old and only 1 of those 3 girls has ever laid an egg (which only happened at 36 weeks old). The other 2 have not laid yet, and I do wonder if the stress and less access to food played a role. Although they had food access at multiple points they would grab a bite and run before rooster or other hens would chase. They would hang out after other chickens went in for the night to get their fill of feed. They were bottom of pecking order. All chickens are same age.
As it happened we had a broody and gave her chicks this Sept. Now 11weeks old, these chicks are integrated in the flock, but THEY are bottom of pecking order, elevating the non-layers in the pecking order, which lessened the stress and we started getting an egg a day from one, hoping the other 2 non-layers follow suit. We also have light in coop, so they get approx 15 hours of light a day. Funny enough, guess who chases and pecks the 11week old chicks the most? Yes, the 3 hens that had been lowest on the pecking order.
Good luck!
