I have some 6-wk old chicks that have never been on medicated Starter/Grower. The lady at TSC tried to sell me this powder to put in their water called Duramycin-10. Well, I haven't given them any of it. I do need to buy a new bag of starter/grower and was wondering if they need medicated or just get non-medicated like I've been giving them. I mean, are they too old to be medicated now? Will they be ok if they're not medicated?