The first thing I would do is get a second hygrometer, salt test it for accuracy and compare it to the incubator's hygrometer. The hygrometer could have gotten thrown off.
Seasonal changes/weather changes cause drastically affect the humidity in the bator as well. If you are having an extremely wet season and lots of ambient humidity, that can affect the reletive humidity inside the bator. During fall and summer I can run dry and my incubator will stay above 30% with no water. During the winter when we are running the pellet stove and the air is much drier it's only 16% ish if I don't add a sponge and spring dry it's about 25%. So that needs to be taken into consideration too. But I would check the hygrometer first as there's a good chance it's gotten thrown off.
