Well after going a month only getting/finding 1 egg every other day in my coop, I came out last night to find two rubber eggs and one that was cracked on the end. Is this a calcium problem? I have 3 year+ hens and the rest of my glock is 18-21 weeks old. I have been feeding half layer half starter feed since the majority of my flock is young and hadn't started to lay. Should I supplement with oyster shell or switch them all to layer? Anyone use crushed lime instead of oyster shell? I hope they haven't been eating the eggs from lack of calcium. I think the one cracked just landed on a hard spot in my nesting box where the material had been dug away. Thanks.