I usually use
Promix, which is devoid of any signifigant nutrients and just has some buffering added to keep the Ph between 6 and 7. If you run a gallon of water thru it, you should just see the extra minerals from the buffering agent and not much from nutrients. This would be my starting point. Adding Perlite (which I don't because
Promix already has it mixed in) won't change your Ph. The only things that will change your Ph are nutrients, which tend to be slightly acidic, bad water, although most soil type of grows will mitigate this problem unless it is really bad, like mine drainage. Any municipal water source should be OK with soil, 95% of the time. When you start adding a lot of other things, like
Cal-Mag, Ph up/down, and even nutes, the Ph is a lot more likely to stray outside of the comfort zone. This is why I recommend using a minimal amount of nutes...adding extra won't make the plants take them up, it just accumulates and causes multiple issues.
Cal-Mag can raise the Ph... most tap water has an acceptable amount of minerals in it, like magnesium and calcium, to make it unnecessary to use
Cal-Mag unless you use RO or distilled water.
This is what I mean by getting the soil "right" before planting, so that you aren't trying to fix problems from the start and can concentrate on growing instead of diagnosing. It's pretty simple, but almost too simple for newer growers to realize that it can possibly work. Most problems are caused by the growers adding too much water, nutes, etc. Get everything ready before you plant, and yo will have a much smoother time with everything. I try to replicate nature as much as possible with lower nute levels and growing taller plants, but you are on the right track and should have a good outcome.