I posted in your 72g thread. I strongly believe that the white lines are not parasites, but rather the slime coat deteriorating and bunching into lines. Your fish are stressed no doubt. I`ve had young angelfish purchased from pet stores develop these exact little white lines shortly after acquiring them. No other fish would develop the lines, the lines didn't look parasitic, and they would usually go away in a few days after the angels were quarantined (no meds, temperature change,etc.). I figured that the juvenile angels were just stressed from the activity or competition for food from the other fish in my tank. I would try separating the discus and not use meds or anything and just make sure their quarantine tank is calming. Leave lights off for a few days, make sure water agitation isn't too choppy, etc. How small are your discus? With juvie discus, you're actually supposed to place them in a small tank for a group (20-30g tank range). Discus juries feel more at ease in a smaller tank. Once they get to about 4-5", you can them move them to a large display tank. My thought is that you have your juvie discus in too small of a tank, they're stressed to the point of losing their slime coat and just need a smaller, much less active tank for a while to regain their slime coat and grow in size. I would advise against putting any meds in their qt tank.