Hole in the head disease


In Memoriam
I have a salfin tang, Emperor angel, and dwarf angel... these three have Hole in the Head disease. Are there any treatments? I know that I am supposing to feed them with sea veggie and broccoli and I have done so for about 6 months now and it doesn't seem to help. Any ideas???
All other tangs and fish are doing well. The Sohal, Archilles, Clown Trigger, etc. are disease free