If you are absolutely sure that his husbandry is correct, and you are feeding him enough food then there isn't much that can be done.

a few questions:

  • does he have enough cover to feel secure in his tank?
  • is there anything at all that happened that might ave triggered this?
  • has his attitude changed all the time or just every now and again?
  • are you sure that you don't just smell like dinner to him? (which goes back to do you feed him enough)