Have a recipe where I want my calcium at or just above 100ppm and a PH of 5.4. My water will be RO. I'm going to add gypsum to the mash to add calcium and I have my volumes and weights figured out. My question is on my PH of 5.4. I assume I have to mash in first, then take my PH reading and then make adjustments with phosphoric etc? Or is my understanding of this really off.