My girls are 20 weeks today. No eggs yet. They are EE's The days are getting shorter and not sure if they will even lay this fall. The question is They will eat as much Oyster shell as I give them. Is there a limit as to haow much they can get? There are 4 of them and if I fill a cat food dish 3/4 full they will eat all of it in a day and more if I gave them more. Should I just offer it here and there or what???