I'm not a chemical wizard by any stretch and maybe I missed something in the last few posts but wasn't the main source of concern...the source of K...avoiding potassium chloride(because of the chlorine.)
And, if you did need an acidifying "boost" along with your nutrient wouldn't potassium sulfate be that source of K. The sulfur content would acidify...would it not?
I'm just throwing things out there for you folks to respond to so I can learn...
...or does the potassium nitrate give you the potassium/nitrogen in the same product and that's what makes it the product of choice?...
"The Poor Fish" circa 1930's: The Poor Fish wouldn't have been caught if he'd known enough to keep his fool mouth shut.