I have 12 pullets that are 12 weeks old. I've had them since they were a few days old. Today one of them, I'm not sure which one, but my guess would be the largest buff orphington, layed an egg. They pecked at it and broke it, but I have half of the shell. Why would they peck at it? I'm guessing because its foreign, or a vitamin defiency? The shell wasn't super thin, like I was expecting, but it was kind of a small egg. They have all been on chick food, should I switch them all to layer now? I thought it would be another month or 2 before they started laying? Thanks for your insight!