This is what happens when you don't quarantine, or use inefffective QT treatments.
That looks to me like Ich (crypto). The animals need treated or you will loose them. The downside to all this is that your tank is infested. So even if you treat the animals and clear them up, once you put them back in the tank, they will be reinfected.
Your only real option is to remove each fish, put them individually through TTM, and leave the tank fallow for a minimum of 9 weeks to ensure the parasite dies off. There are other less desireable options such as:
1: hypo the entire display tank.
2: remove the fish and treat them all at the same time with copper and leave the tank fallow for 9 weeks.
3: treat the entire display with copper. Which will may save the fish but will 100% destroy the coral and every invert and prevent the tank from being anything but a Fish only.
4: take the fish out, treat them separately and tear the display down. Bleach it and start over with new rock and sand.
Sorry man, sucky situation. I don't mean to harp on you, but in the future you must QT your fish, and treat them prophylactically with TTM and formalin dips before adding them to your display or this will just happen again.