I've had a similar issue lately. It's not consistent. Sometimes I can go the whole week and at the end the water will be clear and smelling fine. And sometimes within a matter of hours the water gets cloudy and smells funky. I really have no idea why. I started adding some dutch master zone recently when I refill the rez and that seems to have curbed it. At least for the last 2-3 weeks I have been using it.
EDIT: I'm using GH 3 part nutes, RO water and some cal-mag +