I did a search to see if this was covered already and couldn't find anything similar. Lately my hens (I have 5, Golden comets) have been laying eggs that have a crack along the side. There is usually one each day. It is not on the tip as some others post and it is a lateral crack-- almost the way they crack when they freeze in the winter but it's not that cold yet. They're eating a good pellet food, leftovers and greens twice a day, they have sand and gravel in their run. I mix some oyster shell in with their pellets. I haven't changed anything about their diet, but suddenly the cracks are appearing. They've been good, hard shells for more than a year since they started laying (they're about 18 mos old) Any thoughts?