Baby beardie acting weird - i am concerned :(

So, i have done quite a bit of research and have some experience with friends' older beardies, but i am still a first time owner. I just got my baby beardie from PetCo almost two weeks ago. Its name is Mellon, which is Elvish for Friend, and i seriously love this lil boop boop so much!
When i first brought him home he had some stress marks as baby beardies do. But overall things were going smoothly and he was light in color. However, the past few days, Friend has been acting weird. He (unsure of actual gender) has not been eating as much (only about 4 crickets a day), hasn't been moving around as much, and is generally darker in color except during bath time, and pretty much always has stress marks.
He is only 1.5 - 2 months old (about 5 inches, definitely a little baby). I have a 20 gal tank, a loose substrate meant for desert lizards, a Zilla slimeline UBV light and a zoo med basking light as well as a heat emitter (for night time). His tank is about 95 degrees in the basking spot. I know y'all tend to advise against Zilla and i'm aware of reasoning. i plan on getting a reptisun 10.0 soon as i can. I dont know the humidity level as the reader i was given stopped working and i havent been able to aquire a new one. Other than that, he loves his bath and mainly drinks water during it and closes his eyes while soaking and becomes lighter in color. He doesn't seem to mind being handled, in fact he will usually climb back onto my hand when i try to put him back in the tank, which melts my heart <3 (i mainly handle him when he's sleepy). He eats crickets (dusted with calcium a few times a week) but is totally uninterested in the salad we offer.
We started him on a vitamin supplement yesterday, and after giving it to him, he actually lightened up quite a bit, ate 5 crickets, and was generally more active. But today, he hasn't eaten at all and has pretty much been asleep all day, not moving, looking quite dark with very prominent stress marks. He did drink some water during his bath. He is going to the bathroom regularly and isn't showing signs of impaction or respiratory disease.
Could he be starting the shedding process? Could i be handling him too much? Could it be him seeing is reflection? so many possibilities...
He was doing well for about a week after he got here, and the past 4 days or so have just been off.
Sorry for the long read, but i am super concerned and just want my baby to be happy.

Baby bearded dragons need a high basking temperature to be healthy — between 110-115 degrees. When they're too cold, they can't digest properly and as result have less of an appetite.

What are you using to measure temps? Stick-on analog thermometers tend not to be very accurate; temp guns like the Etekcity Lasergrip 774 are much more reliable.

The Zilla desert UVB isn't very powerful, and also could be contributing to the diminished appetite.

Feeder insects need to be dusted with calcium at every feeding. The calcium dust is not a supplement so much as it is a corrector designed to balance the natural nutrient imbalance present in most feeder insects (I recommend reading Feeder Insect Nutrition Facts for Reptile Keepers for more info).

What is the loose substrate? Despite marketing claims made by manufacturers, loose substrates can be very dangerous for bearded dragons, and especially babies, since they're so small.

Hello,

Are you using a stick on type of thermometer? If so, your temps are probably going to be
off by a bit. As suggested, try to get a digital probe to better measure your temperatures.
I would keep the basking spot range at 95-110 to avoid overheating. The cooler end needs
to be around 78-82 or so.
The Zilla tube bulbs are very weak, so they have to be mounted underneath of the screen
& close to them for maximum exposure. That's why we recommend either the Reptisun 10
or the Arcadia D3 12 or 14% tube bulbs. The UVB output is much better quality.
He could possibly be getting ready to shed because that does affect their appetites some
when they start shedding.
It would be a good idea to change out the loose bedding because impaction is probably the
main cause of impaction, next to feeding too large of insects, in youngsters.
Do you have any pictures of him & of the setup you could post so we could see his physical
condition?

Tracie