I have some babies, between 10 and 16 weeks that have been in with the rest of the flock for about 1 month. They are eating what everyone else eats, including layer crumble, sometimes some dark leafy greens, and scratch. They sure seem fine, but now I'm reading they shouldn't be on layer crumble at this age? Why not? And if I'm to feed them something special, how do I do that when they are in the coop and run with all the other older chickens?