My clownfish has ich right know and I am getting ready to put him in my quarintine tank but his white spots seemed to be over his fin. But my auncle has a pond with koi in it and one of his koi got it and it did the same thing as your trigger but he didn't have a quarintine ank and it ended up dieing. I would put it in a quarintine tank and treat it for ick and see if it goes away.
10 gallon salt water 3 damsels
20 saltwater mini reek yellow tang green mandrin goby, clownfish, yellowtail damsel, coral banded shrimp, skunk cleaner shrimp, lots of corals and fiji rock
75 gallon cycling soon to be reef tank