It's possible that it will take your Blue Acara a little while to recover. He could also be having trouble passing any worms in his digestive tract. Is he eating? I've read in a few places you can try feeding mashed peas to help "move things along".
Unfortunately, it could also mean that the worm infestation is too far along in the Blue Acara and he might not make it. I hope he does.
Even if a few fish don't handle it well, I'd still recommend the three doses.