Sulmet is the sulpha drug, that is the trade name for Sodium Sulfamethazine.
Amprolium is not the only in feed cocci medication anymore, several others are now in use. As I'm in Canada I'm unsure what your Start and Grow would have, but look on the label for amprolium, diclazuril, robenidine, those are common. If you want to use a medication I would suggest selecting one other than the same one in the feed as this particular cocci could well be resistant to it. See your other thread for suggestions.