Hi- I have 21 wk old ladies who have been laying eggs for a few weeks now. Recently, we have gotten an egg with no shell, and today there was two eggs in the box cracked because of thin shells. This has also happened once before. I have been giving them calcium in the form of crushed egg shell and oyster shell, but do you have any suggestions to help with this problem? They are on agway layer feed. Thanks so much!