ILGM Auto NL Indoor Grow (COVID-19 era)

Tuning in the Blumat tropf with goal of moisture meter reading ~100. Still worried about using the tap as water source since I'm pretty sure the pH is too high. A couple sources say the soil should buffer water pH so much that monitoring it is not necessary. I want that to be the answer, of course, since it is less work. And because I put so much effort and money toward getting the tap connection right. (That's sunk cost fallacy, though, right?!) For now I will judge based on health of the plants but since they're autoflower I know any disruption (such as from alkaline soil limiting nutrient uptake) can be difficult to recover from. My first Grow Question was about the pH of water in a reservoir, should I switch to that from the tap. If I fill it with tap water then ensure the pH is correct will that pH remain stable? I think one answer seemed to think I was asking about stability of the reservoir construction/fittings. Instead, I'm asking about stability of pH'd water in a reservoir: how much does it drift over time? How often would I need to keep checking/adjusting it? The alkalinity of the tap water from what I can find online is 'hard water' which I think means decent buffering ability which in this context would help pH remain stable? Shouldn't the reservoir have water bubbling in it? That would increase the pH, though, right? I guess just setting up a reservoir and checking and measuring will give me answers but I'd appreciate any advice. Thanks! Day 17 (night of April 11): I switched the Blumat tropf water source from the tap to a reservoir of water pH'd to ~6. Made sure to bleed the line of air. We'll see if there's a difference. BTW, the moisture meter today read 160 so I loosened things up a bit on the carrots. The leaves did look a bit dry, with mild cupping. Day 18, moisture meter was 190-ish.... Opened up those carrots and raised the lights a bit. pH closer to 7. Left it there but tonight will check and lower it again I'm guessing. I really don't want to do the soil pH measuring process, which from what I read should be combining soil with distilled water and shaking, letting settle, filtering then checking that water. Hopefully the plants will start looking super-happy and I'll continue the idea it won't be needed. Day 19, evening, moisture meter was 111; pretty close to where I'd like it. Still using water reservoir instead of tap. This morning the pH was still around 7; I lowered it closer to 5 and it's about the same this evening. Didn't do any more LST or anything. Waiting for more plant soft wire to be delivered. I'm satisfied with how they're growing so far. Day 20, evening, moisture meter was 199; I loosened the carrot. Continue to use water reservoir; pH tonight was right about 6. Received shipment of plant tie soft wire stuff and did more LST. Raised light a bit after. Coloring overall seems better with pH'd water; not sure why that one leaf was all messed up. Here's a question: Anyone have advice on LST and/or defoliation at this point, based on the pictures? Day 21, carrot too loose! Soil too wet on Plant 1 and Plant 5, moisture meter on Plant 1 was 22. Tightened back up. pH of water in reservoir still good, around 6. Tomorrow is beginning of Week 4!