Less a lizard eats the less it will poo.
Essentially the equation is IN = OUT minus stuff metabolized to make more dragon or new tissues..
I can see a few obvious issues.
Temperatures gauges used are very poor , that type are known to be highly unreliable and extremely inaccurate (can be 25 degrees out !). Recommend you get hold of some digital thermometers like
http://www.ebay.com.au/itm/Aquarium-LCD-Electronic-Digital-Thermometer-Fish-Tank-Water-Detector-Practica-BU/252762165947?_trksid=p2385738.c100677.m4598&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20160908110712%26meid%3D6ac464a2a1b24339be32c744b2ff5cf9%26pid%3D100677%26rk%3D2%26rkt%3D15%26sd%3D201577608563
these are very good for getting a good idea of your tank's warm and cool zone temperatures (and the ones I have proven to be very accurate)
and
http://www.ebay.com.au/itm/Digital-Temperature-Gun-Meter-Laser-Infrared-IR-Thermometer-Kitchen-Outdoor-NEW-/162322033570?hash=item25cb25aba2:g to get your surface temperatures (ie basking spot temperature).
Essentially you have no real idea at the moment what the zone temperatures and basking spot temperatures are , reptiles rely on heat to digest their food , if too cold their metabolic rate slows and they loose interest in eating.
Red heat globe - these are not appropriate for bearded dragons as they change the colour of everything you give him to eat (greens, veg, bugs). I recommend ditching the red globe and replacing with either a good brand MVB (will provide bright colourless (more or less light), heat, UVA and UVB) or a clear colourless par38 Philips incandescent spot globe of suitable wattage.
Can you tell us the wattage of the UV compact globe and it's UVB rating. I think you'll notice an improvement in his appetite if you have a good quality high intensity UVB globe, a change to a 26W UVB200 will help.
You ought to consider installing a 10%UVB - 14%UVB T5 tube with a reflector behind in it the near future.
Inadequate exposure to UVA will result in a reduced appetite and reduced activity in a bearded dragon.
Can you also tell us when the lights are turned on each day and off each day ?
His age ?
His weight ?
And your current feeding schedule (when ? what ? how many bugs each feed ?)
His tank is too small , he'll soon grow too big to comfortably turn around and move about in such a small tank.
Although he's small he's not a dwarf, like a Rankin's .
