Give him a good 5 min bath in room temp water. The mite treatment is the last thing that you did that was different, so that's almost certainly the cause. If he keeps freaking out after the bath, wash out the tank and switch out the bedding.

If mites are still a problem, spend the money on a can of Provent-a-Mite, and treat the ENCLOSURE ONLY with that instead of the Nix.