Dark beard/stress marks, not eating as much, still active?

I adopted Freyja 4 months ago from a customer of mine who claimed she was about a year and a half old and felt bad because she didn't give her much time or attention.

Freyja is 17.5" long from nose to tip of the tail, she is in a 40 gallon tank with 150w ZooMed basking bulb, basking spot is at 110°, and an 18" ReptiSun 10.0 for UVB, her cool side is at 75°, with about 30% humidity in the tank. Her UVB hood used to have a plastic covering which I removed last week; it sits on top of her mesh cover, should I attatch it inside the tank?

When I first got her she was chubby and would eat her salads and supers with no problem. She shed her back legs a couple weeks after I got her, and she had a full body shed about 2 months ago. I took her to the vet a little over a month ago because she was lethargic, not basking, eating, or pooping. She was treated for coccidia with an antiparasitic and I sterilized her entire enclosure and all ornaments 4 times during her treatment. During her follow up they did a second fecal test and confirmed her parasites were gone. The vet told me she was overweight, a 7 on a scale to 10, and told me to offer her salad daily and insects only every 2 or 3 days and that although she probably wasn't eating due to the parasites it could have also been to regulate her weight herself. I have since taken the vet reccomendation on feeding and dust her food with calcium 3x a week and multivitamins 1x per week.

Just in the last 2 weeks she has eaten much less, just a bite or 2 of salad and 1 or 2 insects on insect days and some days doesn't eat anything at all. She is still pretty active and basking and doesn't seem bothered when I handle her, but she has also darkend a bit and has a dark beard and stress marks on her belly. Since she hasn't eaten much, she also hasn't pooped much. I bathe her every 2 or 3 days and she drinks (I also drop water on her nose daily, I doubt she is dehydrated), she also lightens up in color in the bath as they do and seems quite happy. She also lightens in color when I put her harness on and take her to the pet store or coffee shop, which is a new thing we do. Lightens up as in her beard and stress marks are completley gone until we come back home. She pooped just over a week ago and while it wasn't wet and mucusy like when she had parasites, it wasn't as solid as right after she was treated. She only released urate day before yesterday.

Maybe she is stressed because she just needs a larger enclosure? Would that keep her from eating much? Do you think she might just be going into shed? It seems like she would have begun to shed by now if that were the case...

Any help or suggestions would be appreciated by both Freyja and I ?

uvb bulb should definitely be inside her tank, it assures that she gets all the UVB she needs. other than that it sounds like everything is alright and she looks to be pretty healthy to me, my beardie darkens a lot when i put him in his enclosure as well. if she lightens up when you take her out, she could just be bored or just like being outside with you. a larger enclosure would help, or just a little bit more time outside with you would help too

I agree, the T8 should be inside the tank about 6'' above the basking area for best results. It's great that you removed the plastic covering. That was intercepting all of the UVB and rendering the light useless. In the long run, I recommend investing in a 22'' T5 UVB fixture and bulb. Those are better suited for the larger tanks.