If I understand it right they should stay on Starter grower medicated or unmedicated until they are about 17 or so weeks, then they can be put on layer. Kycklingmamma
You can feed medicated all the way to laying age, if you wish. You don't have to, but you can. I've read to change to unmedicated at about 12 weeks old, since by that time, they should have developed immunity to cocci.
