Yes, the alk is quite low. I'm working on raising it up to the correct level by correcting the salinity now, but it'll take a bit since I can only make so much water at a time. And also i forgot to turn off my ato during a water change so that set me back by dropping my salinity even more. Sigh. Live and learn i guess.FWIW, i don't see lowish salinity leading to low pH, unless alk is low.
Additionally, salt mixes don't generally impact the pH of an operating reef tank, unless you allow them to impact the alkalinity in a significant way.