Naso has a white blotch

[SeaHorse_Fanatic]

Could it be this?

Viruses:

Viral infections are caused by particles that by some definitions are non-living. Virus organisms are only able to metabolically function and reproduce as parasites; using the cellular machinery of their hosts.

Lymphocystis Lymphocystis is a viral disease that looks like white to grayish cauliflower-like clumps, typically at the base of fish fins. It's origins, "cures" and spontaneous remission are somewhat mysterious. The condition may just "show up" even in meticulously clean systems.

from wetwebmedia.

Good luck. Going through my own struggles with my male seahorse this am.

Anthony