I think that when you picked out 'egg layers' there are meant to be white leghorns in the bin, and you got cornish crosses. Not your fault, TSC's fault. Because cornish crosses are meant to get big, they really do eat a lot. You were right to limit food for them. Now that you don't have any, you can continue to free feed the chicks. In the future, I would recommend raising chicks in a separate brooder either outdoors or indoors, so that everyone can get their proper feed. This especially goes for if you have hens or chicks with special eating or diet requirements. I am sure that your chicks will be fine, but it's good to know for the future