Is this tail rot?

The Reptisun 10.0 t5 long tube or Arcadia D3 12-14 %. These are long tube bulbs, superior to coil + compact. And just give him time to gain an appetite. What do you feed him ?

Well temperature and lighting play a big role in appetite. Without proper temps, digestion wont occur how it should. And you can see how if hes not digesting, he wont be eating.

Luckily the digital with probe end thermometers can be bought really cheap online or in petstores. This will allow you to read your basking surface temp. Dials on glass dont allow that

As far as uvb, you will need to get a new fixture for it, along with the bulb.
The reptisun 10.0 is a great bulb and it comes in a t8 version, or a t5 High Output version. Which bulb you go with is determined by your setup. How big your tank is, how tall the basking site is, and some other little details that we can go over.

All that being said, it's not uncommon at all for them to not eat much for the first week or two. But it's best to get the setup as good as you can sooner rather than later

I know the whole uv setup can be a bit expensive at first, but once you're setup, you'll be good to go!
And you'll be able to get a new thermometer for cheap at least! Then if you need to raise or lower your basking bulb, that will be easy to do.

-Brandon

Ok thanks guys! And I’ve been feeding him some of this Zoomed juvenile bearded dragon food with mealworms and Romain lettuce

Beardies do love mealworms !! Sadly they are not a good staple, neither is the beardie pellets. Get him some small crickets, bsfl [ Sold as Phoenix or Repti worms which are black soldier fly larva ] or dubia roaches. For greens get some kale, mustard, turnip greens. They will also eat clover leaf from your yad if your yard is not chemical sprayed.