Are they inside or outside? I'm keeping mine on non-medicated while they are inside. They are doing fine. It's when they are moved out that concerns me. I don't know if ACV helps prevent coccidia. I know it's good against lice and other pests. I give mine yogurt or kefir (depending on what I have) which is good for their intestines. I also give mine a natural wormer in their water.
If you are too concerned about losing one, I would put them on meds when you put them into the coop. Just for a few weeks for them to build a resistance to it.
I believe it can be done without meds, or chickens would not have survived to this day and age. I'm just still trying to figure out how. I'm gonna keep trying, but I don't have any really little ones to get sad over the loss of a chick. I'll be sure to post when I find a method that works.
What age do you start giving your chicks yogur or kefir? I gave my last couple of batches kefir at about 2 wks, but my new babies are just a few days old. Is it too early to start giving them small amounts, free choice?