Normally when you add discus to a tank that has them in it can take a week or so for them to sort out the natural pecking order, I've had this in the past, they can sulk, hang out on their own, not eat etc. but after a week or so they are fine.
Do the obvious, big regular water changes if you don't do this already, try to keep it in the parameters it's lived in before, if it's use to ro give it ro as long as the other fish are ok with it, try a 75% x water with 25% ro if your other fish are not use to it, the others should be fine your tank size sound big enough