Is it ok if the tank is at 20-25% during the day then goes to around 45% in the overnight hours?
When I wake I notice it's always between 45 and 50 but goes down once the heat lights come on.. takes about 2 hours but does go down. I'm guessing it takes a while to go up to 45% and he's maybe at that for about 8 hours.
Your humidity is probably fine, it's constant high humidity that is a big problem.
There is the same amount if moisture in the air but when it cools down the humidity goes up. It would be very very hard to keep it the same day and night.