Mold on pipe tobacco

I have had pipe tobacco in some baggies for almost a year now. I have clay discs. I periodically wet them, and place them back into the ziploc bags to keep the tobacco moist. I always use distilled water when soaking the discs. I have never had problems with this method.



That was until I went in to get out some tobacco on Halloween, and two of the 5 bags had mold all over them. I tried to save one of the clay discs by soaking it in rubbing alcohol. However, I figured that it would not be enough to kill the spores, and I didn't want to run the risk of using it in another batch of tobacco and ruining it. I have since removed the clay discs out of the remaining bags.



Has this ever happened to anybody else? Have you ever heard that it's not a good idea to use the clay discs? I've never had problems before, and I've found that it does help keep the tobacco moist. I don't want to start having my tobacco dry out. Any suggestions, please?