My girls will be 20 weeks next week and it will be time for us to buy more feed then. I was wondering if I can go ahead and buy them layer feed then or keep them on the grower until I see an egg. The layer is half the price of the grower. I don't want to mess up there systems or delay them starting to lay. Also should I be keeping oyster shell in there run now? I put some out there last week and they ate it all.