Just didHave you tested any other parameters? like Calcium and Magnesium?
If it's only the Alk, then baking soda would be an easy fix to bring it back to where you want it.
Baseline for the experiment:
5 gallons of HW-Marinemix, mixed for 24 hours at a temperature of about 76 F
Salinity = 1.025
Alk = 8.1 dKH
Ca = 460 PPM
Mg = 1400 PPM
These numbers are pretty close to what BRS says this salt should be. Going to leave it in the hot garage for a few days and then re-test and see what happens.