Medicated food won't cure coccidiostat. You need the right medication. I'm in New Zealand so I don't know what is available to you but (from what I've read) your feed store should carry the right stuff.
The best way to keep coccidiostat in check is to keep the brooder very clean and dry. Dampness allows it to multiply and thrive, infecting your chicks. Also, the feeder and waterer need to be kept very clean as eating their own poop can mean their system becomes overloaded.