Did you guys use vision daily?
If I remember correctly the advice was to not use vision for 1 day a week to let your tank clear out the build up.
I used vision from the day it came out up until about October last year, never had a problem with a build up of gunk. I only used it 4 days a week, even then on the 5th day I would still get the bubbles as the tank cleared any remaining vision.