Very nicely put mate! And nice to meet you!Very true, every single plant I've grown has had it's own thing.
I don't do hydro, where Ph fluctuates like crazy sometimes, but in soil monitoring the Ph is really unnecessary, unless you're reusing or mixing your own soils, and then just get it dialed into a natural range and don't worry about it. It's going to fluctuate during the growing season and tbh in soil it won't matter, autos really don't live long enough to worry it. With photos I might check it once I flip to 12/12 and bloom nutes, but even then that would just be to make sure I'm not building up salts from the ferts in my pots. And if so tbh I'd likely just replant/transplant them to cleaner soil.
Cal-mag is called for depending on your water quality, and whether you have them under full LEDs. I have hard 8+ water but I still needed cal-mag on my first auto grow, so it's good to have on hand. A little goes a long way, buy the smallest bottle you can.
Once you see a deficiency starting in the leaves, then think about whether you can correct it. Look at the charts and keep a close eye on what the leaves are telling you. Some you can correct, others won't show up until your plants are fairly mature and by that time it's not important anyway. (I hear crowds of young voices swearing at me...lol) Eventually if you're looking to grow a cosmetically immaculate plant for a contest or competition, you'll know where to turn, but if you're growing for your own cupboard, remember this is a weed that grows wild and thrives in the roughest conditions. Often the more stressors a plant has during a season, the more gung-ho it is to flower in order to procreate, so a little experimentation to see what works best for you isn't going to do any harm.
Let's put it this way - relax, enjoy the grow, and talk to us anytime something gets weird. There are experts here in every type of growing with autos.