Mine also love hard boiled eggs. Have also given them some cut wheatgrass and herbs, yogurt, compost from my juicer and worms. They seem to love it all. Weirdly enough they are obsessed with the grit i've been giving them too.
@igot4roosters I was wondering that at first as well. I've read numerous places and have been told that it's a great nutritious treat for chicks, plus they love the taste. I always mash it up beyond recognition before giving it to them.
I suppose once they start laying if an eggs breaks and they find that out it would definitely become a problem. I'm not at that point yet so I haven't worried about it.