Chicks are 6-8 weeks old now and need a new bag of feed. They have been eating the chick crumbles. I went to the feed store and they sent me home with a bag if 16% lay mash. The guide to raising chickens say no lay mash until 18-20 weeks. Which one is right? They only sell chick starter and lay mash with several different % protein and that's it. No grower or developer. Are they ok on the 16% lay? I have a little starter left to mix in for transition.