Are you in the Uk or USA?
If in the UK please replace that bulb with Arcadia 12% D3.
If in USA please replace that bulb with ReptiSun 10 (not reptiglo).
Or either would be fine, they are just the easiest to get hold of in whichever country you are! And are relatively inexpensive and last for 6-10 months.
Make sure the lizard can get within 8 inches of the bulb.
They emmit relatively no heat so if youre stuck for fixtures you can even leave the bulb close to the dragon on the floor of one side of the viv, until you figure out a permanent solution. As long as it can get close enough to it.
If you havent replaced the bulb since you got the lizard then you probably should anyway.
Sounds like your dragon is not a youngster, meaning that if he has been exposed to bad UV lighting since he was born (its usually not your fault, most pet shops/unexperienced owners dont know exactly the right kind of lighting to use, and shops sometimes even use the lowest lighting possible as it is cheaper for them and makes the dragon stay small, so they dont have to use as much food) then he is probably showing signs of calcium deficiency.
It makes the dragons tired and lethargic because they have difficulty moving their legs, and in serious cases calcium defficiency can cause MBD (metabolic bone disease).
You see, in the wild they are exposed to mass amounts of sunlight. Thus they have adapted to survive in those conditions. The UV in sunlight helps them process calcium in their body. A
UVB light simulates the sun, and thus allows them to produce calicum. Poor UV lighting can cause all sorts of problems.
Calcium supplements are relatively easy to use and find, and cheap. It comes as a dust, ususally a white powder. In UK id reccomend NutroBall, as it supplies Calcium, D3, and multivitamins, but almost identical products can be found in any good reptile or pet shop.
Basically, the standard way to feed a dragon is to give it as much LIVE food as it will eat in 5 minutes, and repeat this 3 times a day. Well, when its young anyway. If yours is still eating a lot of crickets continue to do this.
When its young, 1 feeding out of the 3 a day is dusted with calcium/supplement, 6 days a week.
For your beardie Id say dust 2 out of the 3 feedings with a little calcium, to help pick up its levels.
If it doesnt eat that many crix then dust whatever it will eat. And sprinkle a little on the veg. (make sure youre not giving it spinach or cabbage, these can bind to calcium and make it so the dragon cant absorb it right, just adding to the problems.)
But most importantly, get that bulb sorted out.
Changing that, making sure he can get within 8 inches of it, and dusting your crickets with calcium supplements 2 out of every 3 feedings should see an improvement over the next few days or weeks.
And if it doesnt seem to be helping, then try to get him to a vet, as it could be MBD.
The faster you act the better
hope this helps!
LIZ