Looks like it might just be Lymphocystis. When clowns get Lympho, it can look that way. See more info & pic below for comparison.
Lymphocystis:
Symptoms - Lymphocystis appears as a white or beige colored cauliflower-like growth that usually starts on the fins and spines and sometimes spreads to the body. Initially it may be small (looks like ich), and then grows in size (which is how you know it’s not ich). Lympho is a virus that many fish carry for life. Fortunately, it is rarely fatal or even harmful to the fish, and symptoms will come and go.
Treatment options - No known cure or treatment exists. However, feeding vitamin-enriched foods and maintaining pristine water conditions may expedite the “going away†process.
