Looks like mold to me. You might be able to clean it with a mild bleach solution, but once the mold gets in the vinyl it might not ever go fully away. Take the head off and clean the inside. Warning, it might mess up the paint, so use at your own risk.
Oh, something else I've used to remove mold and mildew from around the house is Tea Tree Oil. You can get it in the vitamin section of Walmart, and other places carry it. Not exactly cheap, but it's good for lots of other things, like wart removal.
😄
Sheila
