Ok so a few questions.

Do you have some sort of regulator for the uth?

How cool is your room temps?

Where are you taking the temp from?

Balancing a tubs temps is a bit difficult. They heat really fast and cool really fast this is why I have asked about your room temps. Can you get your room to 80ºF that will start to help with temps The problem is then if you have no control (thermostat, rheostat or a proportional thermostat) of the UTH it usually will start to get really hot. the substrate can act as a buffer but snakes often move it aside or dig under it and can (especially in cool rooms) get burned.

Do you have two identical hides? are you taking the temps from inside them? If not you should have and should be. They will generate a micro climate and have different temps and humidity.

More holes in the lid will drop the humidity but worry about your temps first. You might try to insulate with a blanket the tub to try to keep in some of the heat but you will have to keep a VERY close eye on it until you get some regulator on the uth (thermostat is likely the best option if you room temps change at all.)