I have the Large Signature Carly and have been using it for a while, but I noticed a few spots on the bottom of the bag where it is not as clean as I would like it to be. I want to keep my bag in immaculate condition, but how do I clean it? Is there something you should use to keep it clean? Do you send it in for cleaning? This is my very first coach *with tons more to come!* and I want to make sure I treat it right. I love my bag. Thanks so much!