Just going by that pic, it looks like ich and also possibly ammonia burn....looks like his "skin" is shedding.
Cryptocaryon irritans (ick) is a parasite. It must come into the system from another fish. It doesn't "appear" on it own regardless if the fish is stressed or not. There is also no scientific evidence that it can go dormant. It's either in the system or not. If can be present, but healthy fish can fight it off and not show signs. Put a weak or stressed fish in the tank and the ich can show up in full force.
On the other hand, you can take a fish which has been cured of ick, either by hypo or copper, put it in a 1 gal
fish bowl and even tho it may be stressed to the max being in a little bowl, it will not get ick from the stress. If the parasite is not present, nothing can make it appear.