I'm beginning to integrate a couple different age groups into one large flock for the upcoming winter months. Group 1 is 16 weeks old and is not laying. Group 2 is 20-24 weeks old and some are laying, others have not reached POL yet. Group 3 is 1-2 years old and are laying everyday. Right now for group 1 is getting nothing but chick starter. Group 2 I'm feeding them a chick starter crumble, with oyster shell free choice for those already laying. Group 3 gets a layer pellet. Should I continue to offer both kinds of feed, starter and layer when I mix the flocks; with oyster shell for those who need it? Or should I switch everyone to flock raiser (I have never used this before, what is it?) and supplement with oyster shell? I'm worried about the younger hens eating the big girls food and getting too much calcium, or the older girls eating the baby bird and the opposite happening. Advice?