My three-week old chicks have been on the floor of the coop with Mama hen, where I have chick starter for them. My other hen has the roost and counter-top area where I keep layer crumble for her. I am seeing indications that the little ones are spending time up above now - huge amount of layer feed gone. Should I replace it all with chick starter so the little ones get the right food? Also, since neither Mama hen or my recently-ill EE are laying at the moment, I removed the oyster shell from the run. Is it dangerous for chicks?