New Grower Newbie Needs Help On Low ph

[Heavily Medicated]

Day 74, Promix in 3 gallon pots, Algoflash Bloom nutes in at 865 ppm, two Vision Seeds White Widow Autoflower SCROG, same phenotypes both treated exactly the same, both in Promix from same bag. Promix started out at 7.2 ph. I had my feedings where I fed at 6.5 and my runoff was at 6.5 - 6.6, perfect I thought. At around day 60 or so, my ph started crashing on one plant, and coming down fairly rapidly on the other. Plant 1's soil holds about a pint more per feeding than Plant 2's soil. Here are my last 3 feeding stats.

Plant 1: 7 qts in, 3 pints of runoff
In at 6.5, out at 6.3, or a ph of 6.1
In at 6.5, out at 6.4, or a ph of 6.3
In at 6.6, out at 6.3, or a ph of 6.0


Plant 2: 6 qts in, 2 pts of runoff
In at 6.5 out at 6.3 or a ph of 6.1
In at 6.5, out at 6.2, for a ph of 5.9
In at 6.9, out at 6.1, for a ph of 5.3

Plant 2 is starting to show some early symptoms of lockout, singed leaf tips, yellowing between veins, and some necrotic patches on some lower leaves. Obviously,, I raised the ph of my feed to try to influence a raise in the soil ph.

I really do not know if I should wait and see, or do a flush on Plant 2. If I flush, do I need to do the whole 3x pot size = 6 gallons, or would a lesser volume get me to where I want to go?

Please, anyone with experience chime in.

Thanks.

 

[turtle360]

Do you own an Accurate 8?

 

[Heavily Medicated]

Do you own an Accurate 8?

I do not own an accurate 8, but I am going to order one tonight.

 

[Trapper]

I do not own an accurate 8, but I am going to order one tonight.

It's sooooooo worth it.

It's just more trustworthy data than the run-off method...so many things can cause variance with the run-off test.
No guessing with the Accurate 8.

Plus, it can tell you the pH in the bottom of the pot versus the top of the pot. This is useful to ascertain whether
you have nute build-up due to insufficient volume of feedings. (Not watering to enough run-off)

 

[turtle360]

Measuring soil ph via runoff is bullshit. Or to put it nicely, an old wives tale.