
Alternatively they may have decided to supplement their diet with their own eggs, and they may be the egg eating culprits themselves, but they do tend to eat everything, shell and all.
There are various things that put chickens off laying - heat, wet, cold, a bad mood

Magpies, large rats, pine martens, crows will all crack and eat eggs too, so you may have an external culprit.
Are you chickens singing egg delivery songs? We had problems with chickens eating eggs and got in the habit of nipping in quickly when they started to sing out so they did not have the chance to tuck in, and they have stopped scoffing them now, as they simply don't expect them to be there anymore.