What starts a hen egg eating?

[aart]

So far, when I switched up the housing for the three suspected miscreants, I’ve seen no more eaten eggs. And the Marans hen hasn’t done it since, either.

Could have just been a glitch of 'opportunity'....weak and/or broken egg got them interested. Was shell of eaten eggs still around for inspection, was the shell thin? 'Weak' eggs are fair game for eating, IMO.
Unless it is ongoing, I wouldn't worry about it too much, or add supplement 'solutions'. 'Boredom busters' that include foods that may dilute their regular nutrition might not be the greatest idea.