Slightly open mouth

Hi there! For about 2 months now my 7 month old dragon has been slightly cracking his mouth open. This doesn't happen 100% of the time and it's mostly when he is in his tank. I have had him go to the vet because there was some slight popping sounds occasionally when he would breath. Got him treated for an RI and he seems fine other than he still has his mouth slightly open.
Setup: 40 gallon breeder tank
Zoo med 10.0 fluorescent light (made it so the wire mesh lid wasn't blocking the light about a month ago) replaced last week (old one was bought in May)
2 100 watt house bulbs (sometimes one is switched for a 75 watt if it's going to be hot in my room)
Lights are on for about 13 hours a day
Stone tile for floor
Decorations include rocks, drift wood, a fake plant, and a ceramic food dish
Humidity is about 25-35% depending on the time of day (used to be about 40% before I got a dehumidifier in the beginning of September. I use a digital hydrometer)
Temperatures- under hide: 100°, basking spot 103°, the rest of the tank has a gradient that goes down to about 80° (I use a temp gun along with a digital probe on the hot side)
Feeding- gets calcium dusted crickets 2 times a day (crickets are frozen)
I offer veggies about every other day. The mix of veggies is mainly made of different greens and squash
I mist all his food with water because he would hate it when I misted him

Sometimes they just sit with their mouths slightly open like that. They often do it to regulate temperature while they're basking but sometimes just sit there with the tip of their mouths open for some reason. It doesn't necessarily indicate a problem. Your humidity levels are fine at 40% too. Their natural habitat has areas that can go up into the 60% range at times. Too little humidity may cause too much dryness in their respiratory systems so you want to keep a reasonable amount of humidity available.

Thanks!