Could have to do with the medicine. I would call your vet and ask.
I have a 100 watt heat lamp and 75 watt heat lamp in my enclosure, along with a 10.0 reptisun
UVB light (the light holder is less expensive if purchased at a home improvement store ie; home depot or lowes) and he is about 2 months old and 10 inches long including tail, and in a 55 gallon fish tank. His lights have melted the plastic siding of the fishtank before, but only if its directly overtop of the plastic edging for a good amount of time.
His temperatures are perfect all day every day, if that gives you an idea.
You should invest in an electronic thermometer, they run about $20-$40, (plus shipping if ordered online)
Also, are you making sure he gets enough vitamin? you should dust his crickets in calcium at least once every other day.
In my opinion a 55 gallon aquarium is a good size for a growing beardie, it doesn't stunt their growth like smaller sizes (which i think sounds unhealthy) and they have so much more room to run! I got my 55 on sale last year for $50 (they can run up to $140) and they seem to go on sale a lot throughout the year,.. also you can check craigslist, or even ask family and friends if they have any extra they are willing to sell (easy way to ask-- facebook!)
bearded dragons are expensive. We have only had him almost 2 months and here is my estimated list of costs...
Tank $50.00
UVB Light $20.00
UVB Light Case $23.00
Basking Lights $25.00
Light Fixtures $22.00
ReptiCarpet $20.00 (DO NOT use sand, you can use newspaper, try to tuck edges in so he doesn't eat the edges)
Calcium Dust $7.00
Cricket Gel $7.00
Water Bowl $10.00
Basking Spot $20.00 (bought a decor tree from petstore)
Leaves $10.00 (I bought some from craft store, washed them, and hot glued suction cups on)
Cricket Bin $5.00 (use storage bin to save money, poke holes in the top for air, crickets also last longer.)
Feeding Bin $5.00 (you can use normal storage bins to save money)
and at least $200.00 in crickets thus far, but would only be about $75.00 if I had ordered crickets online the whole time
and keep in mind... thats not everything I'm using... just what I feel are the essentials..
(lets not forget the $98.00 vet bill when his eye wouldn't open up)