Im with nu nu. Does not look like ich. More like a blotchy discoloration which can be from any number of things. However would keep an eye on it to see if it progresses. If it stays as is i would not worry much, if you start to see it becoming worse then it might be something to treat. Right now your probably just best to quarantine him and see how he does.
29g Mixed Reef, 150w 14k Phoenix MH w/ Moonlights, Reef Octopus BH1000 HOB Skimmer, Ecotech Vortech MP10es, ReefKeeper Lite (Plus), PH Probe, Temp Probe, ATO, Carbon/GFO Reactor.