Those dial-type thermometers and hygrometers are notorious for giving false readings, even if they don't make it so obvious as your is doing. They tend to read low temperatures when it's really waaaay too hot, and higher humidity than the air actually has, which gets your husbandry all screwy, not really through any fault of yours. I'd pick up an Accurite digital thermometer/hygrometer from your local pet store, or some people suggest Walmart might have them. The internet is my best friend for finding things like that.