I have 2 older hens about 28 weeks old, still not laying. One that is about 19 weeks old, not laying. And three that are 13 weeks old. They have all been on the grower crumbles with some scratch and various scraps of vegetables. I am ready to give the older ones the layer feed and shell--either ground eggshell or oyster. But I read that it is dangerous for the younger ones to get the calcium while growing. And I heard that its best not to give the layers the medicated grower feed. I am not sure how to proceed with feeding them, especially since I'd like to get some eggs coming in before it gets too cold around here. Any suggestions for this new chicken gal?? Thanks in advance, I will check back as soon as I can.