Definitely not Marine Ich
That would present itself as specs, just as what sand specs look like ... dots.
And the worse it gets, the closer it looks to being covered by a salt shaker - or a whole bunch of pimples - whatever helps you visualize it
I've blown up the pic and what I see is damage, such as maybe an impact with corals or rocks. But I could be totally wrong ...
When you look at the fish, do you see anything that looks like it's on the outside of the fish ? You're looking for a parasite that would be prevalent as an external bump, or something trailing as if it's attached and trailing backwards.
If all you see are bumps/abrasions, just keep your water quality pristine, good foods, and it will heal with time.
Use Google to peruse the millions of pics of Marine Flukes, and other such parasites including Parasitic Copepods.
Could help you, but I still feel it's damage from contact with something pointy ...