I don't know how or why PH is that low, apart from liquid chlorine and topping up with fresh water (evaporation and back flush), there has been nothing else added to the water. I was expecting it to be super high, not low.How did the pH get that low? Your PoolMath logs shows a TA of 75 (that would be 80 as you cannot measure a 75 with a drop based kit). Very hard to have a low pH with higher TA. A little aeration will drive the pH up quickly.
My Clear Choice TA test says One drop at a time, add the total alkalinity titrating reagent. Mix between each drop, and count the total number of drops added until the colour changes (usually to red, but possibly also pink, yellow, or clear). If you are unsure whether the colour change is complete, add one more drop – if there are no more changes, don’t count the extra drop in your total. Multiply the number of drops by 25 to get your TA level in parts per million (ppm).
I added 3 drops multiplied by 25 = 75