Do a search on egg eating, you will find many many posts on it, and lots of good suggestions. Some work for one person but not another.
i adopted some hens once, the owners said they weren't laying much, probably due to the cold weather. Well, they laid fine. But they all gathered around the hen that was laying and pounced on the egg the second it hit the box. It was a little creepy. They were like vultures. i even stood there once, ready to snag the egg the minute it was laid. i had to fight off five crazy hens (even the one that just laid) frantic to get that egg first.
i tried blowing and filling the eggs with mustard, hot mustard, wasabi; covered the nest boxes to keep them dark, used wooden eggs. Nothing worked for me except getting rid of them. i could never merge them into my existing flock and have everyone eating the eggs.
Good luck. Hopefully you have caught this problem early and some of the great suggestions here will help.