Brad, Jon? I don't know, but I think you guys use Kent. Have you measured the alk of your replacement saltwater?
The problem has been fixed by buffering. I am also stunned by the rapid disappearance of the cyano. However, since I never did it the first four years, it is odd that my newly mixed saltwater is so low in alk.
As I say, I always measured tank alk at nsw values previous to this.