Baby beardie not eating

Hi, I got my first bearded dragon about a month ago and he's not been eating great. We started off feeding him small dusted crickets and gradually he lost interest in them. Whenever we put the crickets in his tank he would get really dark stress lines and he would get too stressed in a separate eating container. While waiting for some medium sized phoenix worms to come in, we had to feed him some wax worms which he absolutely loves (I am aware that these are awful for a staple, we didn't have any better options around us that he would eat and had to wait a week for the phoenix worms to come in). He ate a bunch of phoenix worms when they came in, probably around 10 the first day and 7 the next, but as the days went on he gradually stopped eating them and he now only eats 1 or 2, if any. I tried mixing the phoenix worms and wax worms to trick him, but he ate right around the phoenix worms! We've stopped offering wax worms in hopes that he will eat the phoenix worms, but he hasn't really eaten any so we decided to make a little "worm smoothie" and drip it on his nose. He seemed to like it so I was wondering if this was a good alternative until he forgets about wax worms and eats live phoenix worms?
His tank is a 20 gal at the moment, he's around 6 inches long and seems to be really small for his age (got him from a pet store, so I'm guessing by his size that he's around 2 months). His basking area stays around 100-120 and he has plenty of space to move if he gets too hot, and his tank stays around 80. We have the sticky thermometers but also just got a temp gun for more accurate readings. We got the zoo-med kit but decided not to use the sand and got a humidity gauge which stays around 50%. The UVB is a reptisun 5.0, I believe it is the tube kind but I'm not sure. He has a hammock, log, and cactus on the hot side and a half log hide on the cool side. He always has a few worms and greens in his food dish but doesn't seem interested. We previously had to use a red light for nighttime but just got a CHE so we don't disturb his sleep. He's super alert and runs around his tank when he's not basking and poops every day. He seems healthy to me other than he looks a little thin.
Oh and the smoothie he had today was collard greens, a little strawberry (he loves those), a tiny bit of calcium powder, and a few phoenix worms. I added some water so we could drip it on his nose. He lapped it right up and was drinking from the syringe until he started backing away from it. I put a wax worm in his bowl to see if he was really full or just being difficult, but it seems he's full. If I do another smoothie, I'll put other veggies instead of strawberries in, I just wanted to put something familiar in it. He doesn't look like he's shedding, but he does have stress marks sometimes. He could be trying to absorb more heat but we just moved his tank so it could also be that.
As I'm writing this, I just saw him gasp and puff up his belly, but nothing happened. It's been about 20 minutes since the smoothie. He doesn't appear to have stress marks right now and is acting like nothing happened, so maybe he was just trying to look bigger or something (my family is moving around a lot right now). Just thought that was something worth noting.
I was also wondering if I should get the large phoenix worms next time since they look more like wax worms.
Thanks for your help in advance! Glad to be part of this community, it's helped so much already!
Here's a pic of him hunting for a wax worm (his name is Chalooby)

He is small but looks healthy. He's a cute little guy =). It's best if he hunts down his food on his own. It's possible he's being picky with the bugs and it's good that you're limiting the wax worms. He may also enjoy silk worms if you add those to the mix. Just keep trying rotations to try and get his interest.

I suggest keeping the basking surface no higher than about 110. 100-110 is about right for that and there should be a gradient down to about 75-80 or so on the cool side. The UVB light is a problem. The 5.0 bulbs are lower output and not really suitable for bearded dragons. In a 20g tank your options are a bit limited. How far is your light from his basking spot? What kind of fixture do you have for the UVB light?

The UVB hood is the naturalistic terrarium hood also by zoo med. It sits right on top of his tank as close to the heat lamp as we can get it, probably 5” away from his highest spot. We also fixed the basking spot, it’s now around 100-110. Thanks for the suggestions and I’ll fix that UVB asap!

OK so that's a dual bulb fixture for the UVB. I'm glad you aren't using the red bulb that comes with it. A CHE may get too hot for that fixture so keep close watch if you give it a try. You don't need if it overnight temps stay above about 65 or so though. CHE may need it's own dome. For UVB with that fixture, I suggest using an Exo Terra 26w UVB200 (wattage is important, 13w is too weak). That should provide adequate UVB at that distance. You'll probably want to start planning a larger tank for him (4'x2'x2' or larger) as an adult and I'd go with a T5 UVB light and fixture at that point. That's a few months down the road though (or earlier if you want to).

Yeah we do actually have a separate fixture for the CHE and the UVB has a separate fixture too, it’s a long hood type thing. The heat lamp is the double fixture with the red light but we aren’t using that. Sorry if I misunderstood or misspoke earlier. Thanks for the dimensions lol we are planning on doing a custom tank but aren’t sure how big to make it. Thank you so much for your help! Hopefully he’ll start eating again. I also noticed his leg is in shed too so maybe that’s playing a small part.

Yeah that could be. It's common for their appetites to go down and their moodiness to increase during a shed.

He’s been eating around 7 medium Phoenix Worms a day for these past few days!! I’m so happy. Hopefully once we get his new UVB set up and his leg is done shedding he’ll eat more but this is so much improvement so fast. Thank you again for your help, I was getting so worried!