Did he move from a spot where has has been for awhile, or is he relatively new?
Once Nems settle, they stay until their environment negatively changes. Any light, water, flow changes in the last week before he moved?
If the tank is less than 6 months old, water stability and range should be checked firstly. Nems do like stability in water representative of a tank 12 months or more older.
Keep in mind that IMO, many Nems are over fed, if your giving a 3-4" nem a piece of food, it should be no more, than a 1/4" cube, and once every two weeks is more than plenty.
Nems get 75% of nutrition from their zoo processing, same as corals, or at least the photosynthetics which represent the vast majority.
I would stop feeding him but make no other change unless important.
Watch what he does, you have no control anyways, he comes and goes as he pleases, but will instinctively move to a comfortable spot.
Good luck.