Growers/layers feed

We have 2 11 week old chicks and when we let them all out to run together with the older girls, they run into the other coop and eat their layers pellets, is this bad for them? They have growers pellets in their own coop. And this may be a stupid question, when do you move them from growers feed over to layers feed?  :oops:  is it when they start laying?  :oops: