I have 15 chickens at various ages. Three are 22 weeks, seven are 17 weeks, and five are 12 weeks old. They are currently on unmedicated starter/grower crumbles. Three days ago one of my 22 week EE gave me my first egg, and another one today I have put oyster shell in a small container attached to the inside of the coop near the feeder. My question is whether I should keep on grower until this new bag of feed is gone or do I need to chuck it and just offer layer feed? The shells on both of these eggs seem strong. Thanks for your info!