I keep my LV bags in the box they came in in my closet. I was in a hurry the last time I was changing bags so I just threw it in the box without the dust cover and forgot about it. Last night I was going to put another one away and then I remembered my MC speedy didn't have a cover on it so I picked it up and noticed there was like a white powdery substance on the handles and they felt damp to touch. It wasn't damp when I put it in so I thought it was strange. The powder came right off. Any idea what could cause this? It's never happened before. I checked my other bags and they were fine. Should I not store them in the box anymore?