Thank you for your replies. I guess I may have to treat the whole tank. It seem like some of the others are starting to act weird. Not sure if it's because of the tank is heavy planted that causes them to act independent... I thought Discus are a school type fish where they hang out with each other? Suddenly it seem like the Discus in my tank like their own little space and just stayed still.
Just making sure, this med would not effect the smaller fish right? like guppy, pleco, otocinclus catfish? it would just treat them as well. I am a bit scared to treat the whole tank, don't want to murder all of them.