Here is my best solution. Start feeding the whole flock All Flock Feed. It doesn't have extra calcium, so you can feed it to roosters and non-laying hens and pullets. Then use crushed eggshells or oyster shells to give the laying hens extra calcium. Leave the oyster shells or eggshells in a separate container and the hens will eat it when they feel like they need it. Chickens know what they need, so most often the roosters and chicks won't eat food with extra calcium if they can help it.
You could also try feeding the hens and chicks at separate times or places or something similar. Hopefully other members will reply with more ideas.
How old are your chicks? I'm not sure if you know about crumbles and pellets, so please tell me if you want those details.