I believe that egg eating is more a learned habit than lack of proper diet.
It only takes a couple of soft shelled eggs broken in the nest to start them in on pecking all the eggs.
To stop it......
Eggs should be gathered frequently, leaving fake eggs in their place.
Completely clean a nest immediately if an egg has been broken/eaten.
Should never be left long enough for maggots to hatch.
Roll out nests can really help.
It only takes a couple of soft shelled eggs broken in the nest to start them in on pecking all the eggs.
To stop it......
Eggs should be gathered frequently, leaving fake eggs in their place.
Completely clean a nest immediately if an egg has been broken/eaten.
Should never be left long enough for maggots to hatch.
Roll out nests can really help.