There are some hens who become egg eaters. Maybe one got accidently broken, and they tasted it. The problem is that once the hen learns that they can eat their eggs, they will continue to eat them. If there are other chickens around when she cracks them and eats them, they will learn to do this, too. You need to separate her so she doesn't teach this bad habit to others. Do you use plastic eggs in your nests with young pullets? It helps prevent egg eating. A young chicken will try to eat different things. So, they will try pecking at the plastic egg when they are young only to find that it is not good to eat. Eventually, they totally lose interest in eggs. So, when there are real eggs in the nests, they aren't interested. Always try to collect eggs thru out the day and never give your chickens eggs unless you cook them. Don't just throw down a cracked egg for them to eat. You need to make sure there is no connection that the egg you are feeding them looks like the ones in the nests. You can google this topic for more information.