Flush them
Sounds like you had some water sit and get a bit funly on you. I've never had fresh water produce that smell, just salt. I'd consider emptying them, flushing with fresh water with a water purifier additive, then rinsing again. If you can take the boat out for a ride fill the tanks enough with the purifier and let it slosh around during your ride. I'd empty and rinse when I got back. Good luck.
