Yup, you can't keep them separate. Everyone gets starter/grower and then put oyster shell or other calcium (smashed egg shells) in a separate container. The hens that need the calcium will take what they need from the separate container.
I just had a broody hen hatch 9 healthy chicks. I set out their own little chick feeder and chick waterer. But on their very first day of life, mother hen had taken the chicks across the coop to the big chicken feeder and was taking food out of it and dropping it on the ground for her baby chicks. I knew this would happen so I had already replaced the food in the big chicken feeder with starter/grower.
Don't take any chances. The calcium in layer feed will hurt the baby chicks. Give everyone starter/grower, put out oyster shell for the adults and then you don't have to worry about it. Anyone can eat from any feeder and everyone is safe and happy.
Guppy