Search for the roll away nest on this site. The nest box is tilted just enough that the egg rolls away under a false back of the nest. If they cannot reach the egg, they cannot eat it.
You might try putting golf balls, fake eggs, old light bulbs and just about anything else round and the right size in the nest. They peck on enough junk, they will get frustrated and quit.
Make sure your chickens are getting enough greens; they love weeds and grass. Also, make sure they have plenty of oyster shell.
Are they over crowded?
Solve these problems first.
Rufus