Winter shutdown in summer?

Question
We live in China and have a bearded dragon who is about two years old. After the usual daily behaviour of basking and eating he has , for the past two weeks, basically been hiding out under his cave...he opens his eyes when someone walks in the room and if I drag him out he looks alert and stands on all fours peering around but eventually makes his way back to the cave. He has not really eaten in probably two weeks but has accepted water by mister several times. He has probably defecated once or twice a week since he slowed down.  
He lives in an aquarium about 40'x20'x15' with over head Eco Terra coil type 10.0 UVB lighting on one side of enclosure (10-12 hours a day) and an over head ceramic heater on the otherside 24 hours a day....temperature is around 85-90 F maybe a bit cooler on the other side where his bark cave is.  He has a diet of greens and super worms.  The ground cover is reptile sand and we clean it everyday with a hand held sifter.  Prior to this shutdown (or I would like to think that this is what it is and not that he is sick!)  he ate greens every other day or so and five-ten worms a day.....now he really isn't eating at all.  He doesnt look obviously sick but his behavior has changed a lot and we are worried. of course in China it si not so easy to find anyone who would know what to do or say regarding this matter.  We got him from a reptile store , when he was between 4-6 months old.  Hope you can provide some answers or ideas for us, seems like he is in a shutdown but the fact that it is June and his cage temperature has not really changed makes me concerned.  thanks Kahla

Answer
 He may be protecting himself because of the UVB source.  Coils and compacts can cause photokeratinosis.  Get rid of the coil and get the linear fluorescent tube.  Basking should be 100-105 F and the cool end should be in the seventies.  He needs a bright light to bask so use a plain household incandescent bulb for brightness and use the ceramit heat emitter only at night durng the colder months.