Your ph runs about .15 higher than mine(jealous

). I rarely get into the 8's. I run 2 part brs recipe 1 ( sodium carbonate). My dosing schedule is on a 24 hour cycle , 27 ml of Alk /12 doses, calcium is 65 ml / 12, vinegar 60ml /20. Reading your results I am thinking about changing to a 12 hour. I will have to see if my doser allows this per channel or if it is the same runtime for all. Optimally vinegar in the day, alk at night. My ph probe is on the return side of the sump. I found the skimmer side to come up way too low I am thinking due to bubbles. I need to check if my ph probe is long enough to make it to my tank, I would wonder if the flow and potential bubbles skew my measurements.
What do you keep your Alk at? I keep mine on the low side 7.89-8.05. I have considered raising it .5 Dkh.
I know ph fluctuation is "bad", but so few people have the ability to log their ph I have found little on what amount of ph fluctuation is normal and when it is too much. My eyes are my best instrument. Just fun to really figure out. I too have heard that ventilation can have an effect, my tank is in a very open area and has air access to about 4k feet.
Update: doing some randy Holmes reading sounds like fluctuation in the .1-.3 range is ideal.