For some wrasses (Coris aygula for example) this is a feeding strategy. In other species, it is a sign of gill flukes. I stopped ordering Macropharyngodon wrasses many years ago because they just aren't very sturdy, so I can't tell you if they feed this way or not....but I think not.
Prazipro can often be used in a DT, as long as you dose it as per actual tank volume and you apply lots of extra aeration. I hear people say "wrasses are sensitive to prazi". I've never seen that myself, but as I said, I don't work with this genus of wrasse any longer. Two issues with prazi are: dosing without good aeration (not just water circulation) and then dosing a fish too late, when a fish has a very heavy gill flukes infestation, you dose with prazi, all of the flukes drop off, leaving hundreds of tiny holes in the fish's gills, and the fish bleeds out, becomes anemic and sometimes dies.
Jay