What else is in the tank? Sudden bleaching would make me think temperature, but you could rule that out if there are other inhabitants that aren't affected. Slowly add more RO water to your tank to bring your sg back down to 1.025-6. Are you usign a refractometer or hydrometer? If you use a hydrometer, it likely is not accurate. Take it to LFS for them to compare to refractometer or calibrate it yourself:
http://reefkeeping.com/issues/2004-06/rhf/index.php