Is there any possibility that there's a problem with the feed being moldy or stale? Even if there's nothing wrong with the nutritional balance of the food, if they don't like it and aren't eating as much, that could also make a difference. Can you tell if they're eating just as much feed? Or are they eating less?
You could try picking up a bag of what you used to feed. If that was the problem and you caught it before it was a solidly ingrained habit, it might resolve on it's own. At the very least, I'd give them something with good protein and something they'll eat right away.
Did you change to a different type of feed or just a different brand? Is the new feed a layer feed with calcium? Do you provide oyster shells as a supplement? You could make sure you're doing that.
Do you give any other food? Like scratch? If they overeat foods without enough protein, that can unbalance the diet enough that they'll want to eat the eggs.