Dr. - have you ever had issues with the Potassium Sulfate you linked not dissolving completely in water? I read the info on their website and it said 0-4% potential insolubility. I had a small-ish amount of brown matter undissolved. I bottled the dissolved part of the gallon and used as directed.
I DON'T USE ALPHA CHEMICAL
I like Kelp4less and build a soil to source my nutrient chemical needs. Kelp4less has a complete dissolving line of sulfates.