By the way, if you are not routinely maintaining your parameters (at least Mg, Ca, Alk) I would recommend you consider some method of maintenance. I wouldnt rely on any salt mix to do that for you.
Your alk is especially important as it is reflective of the buffer capacity, or ability to resist large swings in pH, of your seawater.
If you are not already doing so, consider one of the many methods. . . 2 part, reactor, etc...