So, it says to wash it every six months. I tend to wash it more frequently than that, but maybe every other month. I washed it yesterday with water only and let it sit out to dry. Today, it smells soured and like mildew. This has never happened before and I'm not quite sure what to do to fix it. These things are supposed to last a "lifetime", whatever that means. Anyone else have this problem? What can I do to get rid of this smell?