The sailfin has classic HLLE. There have been only two studies run on this malady (full disclosure - one was mine) and carbon was the smoking gun. All of the other "causes" stem from misinformation and one flawed study by George Blasiola back in the 1980's. It is NOT caused by stray voltage or lack of vitamin C. Changing the diet can't hurt, but also does not cure it. Even removing carbon won't help because the carbon dust is still in the tank, and in some cases, the lesions are just too deep to heal.
HLLE survey results:
A chevron tang with HLLE on its left side only, right side was clear of symptoms In preparation for a research project on Head and Lateral Line Erosion (HLLE) in fishes, I undertook a quick survey of 100 intermediate to...
microcosmaqx.typepad.com
Carbon paper:
Head and lateral line erosion (HLLE) is an acute or chronic, often progressive problem affecting captive fishes. Its etiology is enigmatic. This study examined the relationship between the use of ...
www.tandfonline.com
Jay