Respiratory infection?

[Y33T]

I may be overreacting but lately Bajo has being acting a little off, he seems a little lethargic, most days he is laying around in random spots in his enclosure and his eyes are closed most of the time. When I have him out or have his enclosure door open he’s completely fine and alert, though when I hold him he’s sounds gunky whenever he flicks his tongue out though I don’t see any discharge in his mouth, nose or eyes. He doesn’t seem to be struggling to breathe unless he moves his legs too much where he’d take a deep breath and that’s it. His appetite is unchanged so far.
I decided to weigh him earlier and he seems to be losing weight. He was 535g in September, dropped to 504g early October and now he’s 499g. A lot of these signs matches up with respiratory infection, I want some opinions/confirmation from more knowledgeable people before deciding on taking him to the vet in case it’s something very minor or to do with the setup.

Temps (in Celsius)
Basking temps are pretty low like mid to high 30s, having issues keeping it up lately
Warm end temps are around 32-35
Cool end temps are 26-27
Humidity ranges around 45-55% (he’s an eastern)

Lighting:
50w exo Terra intense basking spot lamp
5.0 24” reptile one UVB T8 (is overdue for a replacement, not producing UVB anymore)

Substrate:
Pine gro Euci mulch and Brunnings coir potting soil (basically coco fibre)

Diet:
High quality Grain free dog food and some veggies and greens fed once a week. He gets calcium + D3 every third feeding. I had been cutting down on the portions for him lately because we was getting chunky and not able to eat all his food maybe an explanation to the weight loss but I want to be sure.

I do have access to a reptile vet there’s 2 nearby closest is 30mins away.