If the undissolved prazi lands on the coral, they may close up, but if you dosed it properly, it won’t permanently harm them. With prazipro, bacteria do use the solvent as a carbon source, so you may get a bacteria bloom (like with carbon dosing). You should be sure the tank has good aeration, run your skimmer but don’t collect the skimmate. If you don’t have a skimmer, run an air stone.
Jay