Skylord meant what is the actual salinity reading that you're calling 'high'?
First, use this link to calibrate your hydrometer. They are notoriously inaccurate. In fact, I have never used one that read correctly.
http://reefkeeping.com/issues/2004-06/rhf/index.php Then come back here and tell us what the actual reading is after you calibrate.
You should be adding plain unsalted RO water to top off the evaporation - water evaporates, but salt does not so the salinity will creep higher and higher as the water evaporates. You should top off at least once a day, but twice a day is better.