The regular light blub is fine for heat, you do not need to pay extra for those UVA basking lights.
If your house is Airconditioned and the dragon is in it, the ambient temps are a bit cooler now that summer is in full force and the A/c is working overtime. If you have checked him and are sure he is parasite free, he may be entering the stage of slowing down to brumate. We have one that heads down this time of year and have already noticed her start to slow down eating and being lazy at times.
I just get a fecal to make sure they are clear and let them do what they want...... it is amazing how well they get along when they decide to slow down, and I will tell you from experience, there is not much stopping a dragon that is shutting down to brumate. Its a whole internal process to them and many of their digestive system actually starts slowing down and turning off before they go to sleep... fighting it only makes them fat and slower.
When I am sure they are ready to sleep, I bathe them and get a good poo out of them and stick them in a shoe box with a cut out hole if they want to come out and put them in the cool end of their tank....I add a soft clothes of some kind like an old sweatshirt, one slept only 2 weeks, one went down for 5 months!!! Each is different, some do not sleep at all, the first time it can be pretty scary for the owner, but they do fine, I do check them weekly and offer an eyedropper of water, some drink in their sleep, so give me dirty looks and hide more.