I have 4 chickens miss rusty quit laying about a month or so ago, belle has been laying soft shelled or none at all, miss rustie i think is still laying by the size of the eggs, but still not positive that they may be belle's and tallula is still laying, but not every day. I bought this HUGE bag of oyster shell (not knowing exactly what it was) that will last me until i am 100. To my knowledge, the chickens have nothing to do with it. They pick up the chunks and spit them right back out (it looks like rock salt). i have put some on the ground and in their food (which they then won't eat) and also have a container in their coop. I have also tried crushing it, what a pain the in butt. It's way too hard. I give them the old egg shells by crushing and baking them (they seem to LOVE these). They do have 3 different kinds of food because they quit eating the one from the mill so i bought another which they wouldn't eat so of course feeling bad i bought another. The one from our local mill they are now eating again. the layena crumbles i mix with water and night before they turn in and they love it that way and the pellets (they don't like) i sprinkle in their run (sometimes they will pick at it). plus they get scraps however, they are very picky (they don't like warm oatmeal, sweet pots, carrot shavings, yogurt, ham, or barley). With all the different food i can't believe they are not getting enough calcium or protein. Oh yeah, i will let them free range often and when i started w/ that i found it does cause them to lay soft eggs (which i don't understand when several ppl let theirs free range and to my knowledge have no problems), but i would think with all the food they get and the egg shells it would be no problem. Should i maybe keep them locked in their coop for a few days to a week and see if that works? I also have not put a light in their coop yet however, all this started before our shorter days did.