I have noticed that when my silicone cupcake molds and crown cake molds sit out without being used they develop a tackiness to them. I have scrubbed them thoroughly to the point where they lose it and sure enough, a while later it happens again. It gets to the point where I am hesitant to even touch them, because then I get this stickiness on my hands that is difficult to wash off. I know it isn't from the sprays because it is on both sides of the molds. Is there a special way these need to be stored? Thanks.