Same thing here - mine seem to be opportunistic egg-eaters. If they drop them and crack them, they often eat what's left. When the birds arrived here in October they were full-grown layers, and they were all short on calcium. Have been having difficulty getting them back to normal-thickness shells. They don't seem terribly interested in the oyster shell. Feeding their own thin-shelled eggshells back to them doesn't help much either. Yogurt and extra protein seem to help some.
Uh, oh, Mikey. Anyone, please correct me if I am wrong, but here's what I would do. For the egg-eaters: Up their protein, a lot. They MAY be eating their eggs because they need the extra protein.
I had one episode, well actually two, of this. The first was when my broody ate two of her eggs. I gave her mealworms one day, canned salmon the next day, and scrambled egg the third. She never did it again.
Second, my kids fed the hens a raw egg (after I told them NOT to ) It was a good learning experience for them, because the next day there were egg shells in one of the nesting boxes. It hasn't happened since, but I have kept a really deep layer of pine shavings in the boxes. What was happening was that the egg would sometime crack as it dropped from the hen (the hen would scratch all the pine shaving out of the way and lay the egg on the exposed wood). So what I think happened, is that the hen laid her egg, it broke, and there you go.
Good luck, get their diets back on track and go from there. I would definitely offer extra protein and extra calcium.