I have 40, 6-7 week old pullets. I have been getting chic starter grower in what I guess is a crumble. Last time I went to the feed store what they gave me was chic starter grower pellet 21%. What is the difference? Should they still be eating the crumble? Do you feed crumble until they are laying age? Then switch to a layer ration? Or is there a middle step? Thank You.