Well... I certainly wouldn't be dosing my tank with medication of any sort based on what I can see in that photo. The largest white spots nearer the tip of the nose are normal. Beyond that, anything else that I can see looks very small.
As for ich, I have plenty of experience living with that and while my Acanthurus tangs seem to show symptoms commonly, my naso tangs seem completely immune to it. (if it IS in their gills, it doesn't seem to bother them) Naso "tangs" are pretty different than most other "tangs".
Here's a comparison shot of mine... (sorry, I guess that shot is kind of blurry)
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400 gal reef. Established April, 2007. 3 Sequence Dart, RM12-4 skimmer, 2 x OM4Ways, Yellow Tang, Maroon Clown (pair), Blonde Naso Tang, Vlamingi Tang, Foxface Rabbit, Unicorn Tang, 2 Pakistani Butterflies and a few coral gobies
My Tank:
http://www.canreef.com/vbulletin/showthread.php?t=28436