Smooth skinned Acros like the ORA Hawkins tend not to fare well with coral dips. There are other treatments that are used such as interceptor or Bayer insect killer but I have zero experience with them.
I have played around with different iodine-based dips over the years and found that Tropic Marin's Pro Coral Cure works the best in terms of helping to cure tissue necrosis and preventative dip with the least bad side effects.