I just installed a free choice bin of grit in the coop three days ago and put a nearly full bag of grit in it. I noticed this morning its all but gone. My girls are around two months and are on starter feed with very few treats. They have wood shavings in their run and some tall grass pokes through the wire. I've seen them nibble at it but I don't think they've gotten much. Does this rate of consumption seem healthy? I have 14 hens.