I am having trouble getting my humidity up to 70%. I had a egg start to hatch and ended up getting shrink wrapped and dying cuz the membrane got dry and tough. The bottom of incubator is full of water with sponges to increase surface area - on top of this is a plastic rack and then shelf grip paper to keep new chicks from sliding. Then I have a sponge on the grip paper with a steady dropper dripping to keep sponge wet. If I close any vent holes humidity goes up but then so does temp. Any suggestions??