Smell when flossing implant crown?

It's been a week now when I floss under the gum line of my crown there is a foul smell on the floss The gum isn't tender, sore, no ozzing or pain when chewing. Just foul smell upon flossing. What is the cause? Does the crown need replacing? I've been flossing more thoroughly for a few days but it doesn't seem to have made any difference