I have 4 laying hens just barely one year old. They eat Layena, free range a couple hours a day, and get limited treats and veggie scraps. I have oyster shell available in a small dish that clips onto the wire in their run. I will be adding some additional pullets that will be about 10 weeks old when they go in with the the laying hens. I've read that the extra calcium in the Layena is not good for the younger chickens. So should I switch to a Flock Raiser and figure the laying hens will get enough calcium from the oyster shell? Will the younger chicks leave the oyster shell alone if it is accessible in the run?