I have 13 chickens: 1 full-size rooster, 2 bantam roosters, 9 full-size hens and 1 bantam hen. Six of them are about 5 weeks older than the other seven. We ferment their organic feed, and add DE to both their bedding and sometimes to their food. We also feed them lentil sprouts we grow and wild grapes from the vines in the back yard. When the older hens were about 16 weeks, two of them started laying the same day; we believe it was the barred rock and the easter egger. This continued for a week, and then only one egg per day from the barred rock. The barred rock was the only one who used the egg box... about three or four weeks later we got an egg from the brabanter. That was followed by another two days later... The next week we found two in the base of the grill. Then nothing. As we feared somebody might be eating the other eggs, we put a golf ball in each of the two egg boxes... and the barred rock stopped laying. Does anyone have an idea of what might be going on? Should we be adding calcium? We had read that you shouldn't add calcium early in the laying process, and we still have seven hens that haven't started laying yet. Any advice?