How Much Ph Drop From Degassed To Enriched From Day To Night

I have a CO2 injected 80gal Planted aquarium with 130 watts of DIY Cree 6500K LED lighting and a buffering substrate. I currently only drop the pH from the photo period to night by about 0.4 pH or from 6.2 to 6.7. I used remineralized RODI water and I keep the GH at 3 degrees and the KH at 1-2. I use KHCo3 for KH, and CaSo4 and MgSo4 at 4:1 ratios for the GH. I have good surface agitation and I also aerate when the lights are off.
The degassed pH is about 7. I see comments here that you can drop the pH about 1-1.5 in short periods of time. When my pH is at 6.3 during the photo period I have moderate pearling of the plants, but I think I can up my pH, or lower it actually to close to 6.0 or 5.8. I do weekly water changes of about 40-50% and use the EI dosing of Macros and Micro elements twice a week.
I guess the question is "How low can you go!!")

skipd1