This is interesting. I had the same problem. I had 19 chicks and they were getting way too big too fast in the big plastic feeding tub I bought at the feed store. So, I bought another tub and put the youngest and last group of 6 I bought in it. They were lonely, sad and little, so I took 2 other larger ones to put in their with them. They are much older now, 3-4 months older and those two other chickens, the bigger ones not only are very motherly still to the group of six, but are best buds. They sleep in the huge crab apple tree together that is in the middle of chicken yard.