Possible Head and lateral line erosion (HLLE).
http://reefkeeping.com/issues/2005-06/sp/index.php
HLLE does not usually kill fish and affected individuals have been known to survive for years with only mild progression of clinical signs.
Home Care
To correct this condition, a change in husbandry is nearly always required. Improving nutrition combined with removing external stressors (aggressive tankmates and poor lighting) may arrest or even reverse the syndrome.
Treatment with antibiotics alone is unsuccessful, although, resolution of the lesions may be seen with vitamin C supplementation or elimination of activated charcoal from the filtration systems.
Preventative Care
The best way to prevent this frustrating problem is to avoid keeping species that are susceptible to the syndrome. Your pet store clerk and a variety of text books and magazines can help with species selection.
If you do keep HLLE-vulnerable species, then you will want to provide them with optimal environmental conditions, including: a fresh, balanced diet, artificial sunlight, preferred water temperatures and crystal clean water with frequent water changes.
Just some information I came across.
Ken - BWA