If you have jungle parasite clear that has prazi and metro in it. I think you can use it with discus, though others can chime in on that. So many discus have parasites that he almost def has them.
I would hold off on the anitbiotics though, as weak fish may have adverse reactions. If he does get worse and you think you need them, then start with a half dose and see how he reacts to that.
Good Luck!