The product you've been giving them is antibiotics, has nothing to do with treating them for coccidiosis. Put the CORID (amprolium) in all water that is available to them. Instructions and dosing on the package (depends if you get the powdered version or liquid), but someone's sure to chime in with correct dosages. You need to treat for coccidiosis ASAP as baby chickens can literally drop dead before you even realize you have a serious problem. In no way, shape or form, is the treatment for this harmful to your birds or environment. It works by mimicking a B-Vitamin (so don't give B-vitamins while treating for coccidiosis); the coccidia 'eat' the amprolium, thinking that it's B-vitamins and literally starve to death... problem solved. AFTER the full treatment of your flock, add vitamins to all of their waterers for at least a week (can give vitamins every day if you like (unless treating for an illness where it's contraindicated) , their long term health will be much better if you do).
I do not give them medicated chick feed as I have mixed ages, genders and species of birds; I feed 21% protein game bird feed (best that I can get here, but only available in a 40kg (88 pound) bag) with calcium supplement served ala carte on the side. A bag feeds all of my birds for a month.
I start treating for coccidia the same day that I let my chicks out of the brooder so that they can forage in the yard. I treat for about a week and then switch them back to vitamin water. I've had FAR FEWER 'unexplained' chick-deaths since I've started doing this.
