I sometimes have to put a damp (not soaked, or dripping at all!) hand towel or small washcloth draped over a hide or two. Some snakes don't seem to care for humid hides. My guys all hate them! I occasionally have to put the snake inside a smaller container a(make sure it has an UTH with a warm and cool side, just like their cage) and then I put them in there with some damp moss, towels or a couple humid hides.
Get another thermometer that also measure humidity. If you are housing them together, at least make sure you can tell accurate temps and humidity in their cage so you know everything else is controlled. Good job having lots of hides for them! I tell people not to house together, but I know sometimes it isn't easy to run out and get a new setup, so providing them with equally good hiding places should help the stress levels. Do you mist their cage at all? Once you get the hydrogemeter (can't spell... sorry) you can mist the cage everyday and see how your humidity looks.