Yes, switch them to medicated chick feed. The amprolium in it will help them get started on being resistant to the cocci that exists in your local soil. It's not really a "medication", by the way. All it does is block a certain B-vitamin that cocci parasites thrive on. It doesn't protect against any diseases.
That said, "hen" food has calcium in it for laying hens. It's not for baby chicks. Layer feed should only be fed to hens that are actually laying eggs so they can replenish the calcium in their bodies that egg shell building depletes. It's also not high enough in protein for growing chicks.
