First off. Welcome to the forum. This is a great place with a ton of info. Congratulations on your new friend. The more info you provide us the better the answers you will get.

Ok. So high humidity for a little while won't hurt. It's when your super high for days or weeks that you need to worry. How are you measuring humidity? Digital hygrometer or a dial gauge from the pet store? If it's the dial it's no good. Tubs are known for holding humidity very well. You can try drier substrate, what substrate do you have? Coco fiber of some kind? Aspen? Paper towel. Did you we it before putting it in? You can add a few more vent holes to allow more air to leave which will help dry it out. Put the water bowl on the cool side so it's not over the heat pad. Use a smaller water bowl. There's lots of things to try. Pictures of your setup and definitely your new pet would help us. We love snake pictures.