Understanding ph

I have reading a lot about ph to understand it better for my grow and it seems I have learned a few new things:

I should not force the ph to 5.8, rather if it is within 5.5-6.5 I should leave it. I should monitor the ph and check it 1-2 times daily. A range of ph is actually better than being stable because different nutrients are absorbed in different ranges of ph. Above the 6.2ish-6.5ish range and especially over 7 is very bad for plants. A lower ph is not ideal, but not as detrimental as a higher ph.

Seems like ph is very important and prevents many problems a plant may experience. If my ph does remain at 5.8 for example with littler fluctuation should I manually change it myself so it get's a good range. According to the diagram I posted if my ph was stable at 5.8 and only tended to fluctuate up OR down, rather than both ways, would I not potentially run risk of not allowing the plants to absorb either calcium or manganese.

I clearly don't have experience so I don't even know if my question makes sense, but any and all input will be appreciated. Thanks

Another question I forgot to ask. When checking ph in an rdwc system does the water have to be stagnant to get an accurate read, or is it okay if water is circulating/bubbling when I stick my pen in there. Thanks

Everything is can be taking in at 5.8 other than manganese. Which is a micro element used in small amounts by the plant. IE doesn't need to be available all the time.

Read your plants ultimately. But 5.8 is a safe number. If your plant is showing a P def and your solution is dropping PH start at 6.1 and let it drop to 5.6. Reason 5.6 instead of 5.5 is because Mn is available at 5.6 so why wait the extra time for it to drop to 5.5 when nothing else is becoming available and especially since at 5.6 you're out of the range for P and Mg, both major nutrients used and nutrients that you don't want to be out of range for too long in, especially just to pick up some Mn. Its like driving to home depot to pick up some rope to tourniquet your arm that you just cut off instead of driving right to the hospital.

At the same time anything above 5.8 you don't get Ca, another major nutrient used.

For this reason 6.1-5.6 is best swing. I wouldn't let it get to 5.6 all the time though, just occasionally. Your PH may not be dropping now, but it will. Small reservoirs have big fluctuations for big hungry plants.