If you are using an analog dial gauge, then it could be showing you a reading that is not accurate. I would get a digital hygrometer with a probe, they are much more accurate. I got mine on Amazon and it was under 30 bucks.
It takes six hours and table salt to double check it's working correctly, and they can fail randomly. I test all of mine monthly and replace as needed. I work with hermit crabs, and I've watched so many people pull their hair out over low humidity when it was just a bad gauge the entire time! Just google "calibrate a hygrometer" and the instructions come right up. It's mostly for people who put a lot of money into expensive cigars and have a humidor, but it works the same on our pet hygrometers.