Not true on egg eaters! I had the issue and resolved it. It takes diligence on the part of the owner, but it does become a habit, so the sooner you can address it, the better. First, make sure your chickens have LOTS to do. If you do not freerange them, make sure they have things to "play" with in your run. I use a hanging suet feeder and stuff it full of healthy goodies such as cabbage, squash chunks, cucumbers split lengthwise, dark greens, etc. They have to work at it to get the goodies out...giving them something else to think of other than eating eggs. Also, egg eating can be caused by insufficient amounts of protein in their diets. When I had the problem, I made mine oatmeal each morning with cooked hamburger in it for the extra protein. Some folks throw in a few handfulls of dry cat food. Understand that it's not good to increase protein and leave it high. I "weaned" them off the oatmeal/hamburger when the egg eating stopped. I also made a curtain for the front of my nest boxes. Apparently, once they go in & lay and leave, the egg is "out of sight, out of mind." But, the very best thing for you to do to deter this behavior and get them out of the habit is to collect eggs FREQUENTLY. Getting them out of the nest boxes is the best way to make sure they aren't being eaten. If you work full time (like me), you may need to call in help from neighbors or friends who don't work. It's a pain, but it's well worth it. I did not want to cull my egg eaters...I had a few in my flock. All these things worked for me, and it took a few weeks of diligence, but (knock wood!!) I haven't had any trouble since (this was in late winter). Good luck! OH, as far as several using the same nest box, that's perfectly normal.