Yes, please post some photos, as if you have an 18" long UVB tube, it is most likely the weaker T8 strength of UVB tube, and that can create serious issues if it is not mounted correctly. The T8 UVB tubes are at most 15 watts (typically), and as such cannot sit on top of a mesh tank lid, as they are too weak to deliver adequate
UVB light on the other side of the mesh, as they block around 40% of the
UVB light emitted. So most all T8 UVB tubes must be mounted INSIDE the tank, UNDERNEATH the mesh lid. You can do this very easily and quickly by using either the long, plastic zip/cable ties, wire, twine, etc. and threading it through the mesh holes, and then just strap the entire 18" tube fixture to the underside of the mesh lid. ****Be sure that you do this over the Hot Side of the tank, so that the UVB tube is RIGHT ALONGSIDE his bright-white colored Basking Bulb; You want both of these lights to be "sharing" the top of the Hot Side of the tank right alongside each other, then you must position his basking spot/platform directly underneath both lights within the Hot Side of the tank, so that he gets both lights while he's basking. This is replicating natural Sunlight for him while basking.
***In addition, any T8 strength UVB tube must be within at least 6" of your dragons basking spot/platform, as if it's any further away from the basking spot/platform it is not strong enough to still deliver adequate
UVB light to your Dragon. ***Also, you must replace all T8 UVB tubes once every 6 months on the dot, as they have a very fast UVB decay-rate, and at 6 months of being on for at least 13 hours every day (the minimum time both his lights need to be on every day), it will no longer be emitting any
UVB light, only UVA light.
***Also, please make sure that your 18" UVB tube fixture has no clear, plastic cover on it's bottom that is covering the UVB tube inside it; Most don't come with a cover on them, but some do, specifically the Zilla brand tubes, and no strength of
UVB light can at all penetrate any type of glass or plastic, GLASS AND PLASTIC BLOCK 100% OF THE
UVB LIGHT. So if your tube fixture happens to have a clear, plastic cover on it that is over the UVB tube inside the fixture, you must remove it immediately and keep it off.
*****************************I was thinking about this yesterday, but depending on what brand of T8 UVB tube you actually have, this may be the source of his issues. Now if you have either the Reptisun 10.0 or Arcadia brands, then the brand is NOT the cause, as they are the 2 highest-quality reptile light manufacturers available.
HOWEVER, we have long-known that there are SEVERAL COMPANIES who are now making all of their reptile and amphibian lights cheaply in both Chinese and German factories; they manufacture hundreds of thousands of UVB tubes and then brand them and ship them. And as a result of the cheap manufacturing process of these tubes, they often (seems like they ALWAYS do this any more) cause serious health issues as a byproduct of the cheap manufacturing process. Usually these health problems include eye damage, blindness, and neurological damage, AND YOUR DRAGON COULD VERY WELL BE PUFFING HIMSELF UP WHILE UNDER HIS LIGHTS BECAUSE THE UVB TUBE IS CAUSING HIM DISCOMFORT/PAIN/STRESS...This would explain why he's only doing this when he's on his basking spot/platform and only when he's under his UVB tube.
There are many, many brands on this list of bad UVB tubes, I think Knobbys has the complete list, but the most popular/common brands in the US that are on this list and recently have all been causing serious issues that have appeared on this forum are Zilla (now Petco's house-brand), All Living Things (Petsmart's house-brand), and ReptileOne as far as the Chinese manufactured brands go, and then Trixie, which is manufactured in Germany and more popular in the UK, but I found out that Trixie makes any and all types of pet products, from dog and cat stuff to birds, reptiles, rodents, you name it, they mass-produce EVERYTHING PET-RELATED, and the amount of reptile lights they mass-produce is astounding. I went onto their website recently to check them out, and they are shipping to the US and selling a ton of their reptile lights over here now. There are many other brands on the list, but these are the most popular and commonly sold in US pet shops, and specifically Zilla has been causing a ton of problems lately, or I should say "since" they signed-on as Petco's house-brand of Reptile products last year.
So if you could let us know what brand your 18" T8 UVB tube is, this may explain what's going on. Just as a lot of Dragons "Puff-Up" while in a
bath, or under any type of stress, if your dragon is only doing this when he is under his lights and on his basking spot/platform, it could very well be that the UVB tube is causing him distress...
One more thing about your temperature zones, you didn't really answer the question about what type of thermometer you are using, and this is extremely important, because if you don't have either a Temperature Gun or a Digital Probe Thermometer then you have no way at all of measuring his Basking Spot Surface Temperature. Again, you cannot at all measure his Basking Spot Temp with any type of stick-on thermometer, as they can only measure Ambient/Air Temps...
If you are using either a Temperature Gun or a Digital Probe Thermometer to measure his Basking Spot Temp then I apologize, but his temperatures being too low or too high would also explain his issue, and it sounds like at least recently his temperature zones have not been within the correct temperature ranges:
BASKING SPOT SURFACE TEMPERATURE: Between 105-110 degrees F maximum for a dragon under a year or so old; between 100-105 for an adult dragon over a year old...***The maximum SURFACE TEMPERATURE that can be present anywhere inside a Dragon's tank is 110 degrees F, as measured with either a Temp Gun or a Digital Probe Thermometer...
HOT SIDE AMBIENT (air) TEMPERATURE (The air temperature of the Hot Side of the tank that surrounds the basking spot/platform surface; taken by either a stick-on thermometer located in the Hot Side of the tank, or by a Temp Gun or Digital Probe): Between 88-93 degrees F maximum...***The maximum AMBIENT/AIR TEMPERATURE that can be present anywhere inside a Dragon's tank is right around 93 degrees F; this is not as strict a rule as the 110 degree F maximum SURFACE TEMPERATURE rule is, but any Ambient/Air Temperature inside a dragon's tank that is over around 93 degrees F will cause dehydration and can cause Heat Exhaustion if continued for a long period of time, as this also indicated that the Surface temperatures within the tank are going to be higher then they should be.
COOL SIDE AMBIENT (air) TEMPERATURE (The air temperature of the Cool Side of the tank that is opposite the Hot Side of the tank; taken by either a stick-on thermometer, Temp Gun, or a Digital Probe Thermometer): Between 75-80 degrees F maximum...