Can you post a photo of your cham?
I think 89F is too hot, but I'll defer to @MissSkittles and @Beman on veiled care specifics. He's probably opening his mouth (gaping) because he's trying to cool down. He could also be doing this as a defensive posture as well.
what heat bulb do you use?
Hi there, welcome to the forum!
Do you know how old he is?
How much do you feed him/ how often?
What supplements are you using, and what is the schedule?
can you post a photo of his entire body?
@Beman @MissSkittles @kinyonga this looks like a burn to me, do you think MBD is possible with the shape of the casque too?
either way an appointment with an experienced chameleon vet is a good idea.
You could move the hygrometer around to see if you get a different reading in other parts of the cage. Right now it looks like the probe is placed in the open air near the lights. It would be good to check in lower areas of the cage & around the plant.
Knowing the ambient humidity in the room...
What kind of hygrometer are you using? Have you checked humidity levels in different areas of the cage?
Also, do you know the ambient humidity in the room he is kept in?
how long do you mist for?
what typical temps and humidity measurements are you seeing during the day and at night?
Consider adding more live plants to the enclosure, you can get the dragon ledges so you can mount them at different heights to get better coverage.
Do you have a lay bin in her enclosure? How long has she looked like that?
How much/often do you feed her, what do you feed her, and what supplements do you use?