Rasing salinity in 150 gallon tank 1.017

I have a salinity problem I recently check it and it's been at 1.017 for awhile yes I know it's low. I have already added about 60 gallons with of reef crystals and honestly it hasn't really changed it's gone up to 1.018 but yet again I don't have a refractor meter I'm just using the salinity checked they sell at LFS. Please help me guys!