so what was your fix exactly? I just had this start happening to me.. Was it just get her into a bigger res and use some bennies? I'm already using bennies but it does look she's completely filled out the entire bottom 3 inches of my 10gal tote with roots.
My fix was a number of issues.
1. Change from great white bennies to the Southern Ag Garden Friendly bennies. (the most important change and significant impact on roots and ph swing )
2. Stopped using store bought water and bought a zerowater filter.
3. Flushed the fk out of my medium. I had been dumping stuff down there early on in veg, residue was building up and possible acid rain when condensation would form. I ran my circ pump with clean water with a tube rite into my medium for a day and moved it around a bit to clean it all out, than pulled all that water out and put a new soup in.
4. Bigger rez. My plant was way too big for the 5g gator cooler, i moved to the 15g cooler and made an access hole to control my res to no disturb the roots everytime i want to manipulate.
After making these changes, I havent needed to play with my ph at all for about a week and a half at a time. I use my nutes which are around 4.5 PH to bring my ppm up, and my water is at 7 ph, so when im topping off my ph sits perfectly at 5.7 / 5.8 / 5.9 and stays there all week. extremely consistant.
I will post more pics shortly