I have 4 pullets that were hatched on Thanksgiving, 2 RIR's and 2 Black Sex Links. I also have a year old roo. Recently my 2 RIR's combs started turning a deep red, and their wattles have doubled in size (but my sex links haven't changed yet). Based on this, when should I begin leaving oyster shell out? I just bought some to have ready, but I'm not sure when to start leaving it in the coop. Below is a picture of one of my RIR's, and one of my Sex Links, for comparison.