that he is just sort of brumating?
my juvi vittikins sometimes sleeps all day...sometimes is up...sometimes eats...most of the time he digs out a little dark cavern underneath a large stick in his cage and sleeps. i was worried about him for a while but i think it's just cause i didn't give him a "cool down stage" and this is his form of brumating. he has an uth but at night the temperature in the house is turned down to 60, and i'm sure it affects him. also, there are lots of windows around here, so regardless of what cycle i have his lights on he knows when it gets dark outside...sometimes i wake him up during the day and he will get up on his stick and bask and eat a few pellets. i don't like to feed him a lot of veggies when he's like this because i don't want to waste them...he eats the pellets fine, though. i often leave some waxworms or some crix (with jumping legs pinched off) in a deep bowl and i will find that he has eaten them within a couple of days...
if you are really worried, you could try some parazap. it will work on many parasites and even if he doesn't have parasites it should give him energy and stimulate his appetite.
good luck,
amanda