Hi, we're new to Back Yard Chickens, but wow! What a great site! We're doing the best we can to give our recently acquired RIR hens great nutrition, so any suggestions are helpful. We just got them, so they're a bit restricted right now until we're all settled in. We have alfalfa, selected kitchen scraps, oats, egg layer, oyster shell, grit, linseed meal, and have started fermented mash. But our specific question is about rock dust - the kind you would put on the garden for extra minerals. We haven't found enough on the internet to make an educated decision about it. Any advice? Thanks!