SUDDEN pH change after flip

Hi all, I'm growing in a hempy bucket and all during veg I would have to adjust the feeding solution down by 1.0 pH (4.8 pH solution) to get the proper run-off pH (5.8 run-off). After I flipped to 12/12 a few days ago I noticed my pH was suddenly 4.0 in the run-off. What gives? I'm assuming it has everything to do with the flip.

The plant is showing a little stress in some small brown spots on some of the leaves. I'm adjusting the pH up each day by .5 to try to get back within the correct range. Am I doing the right thing? Should I be adjusting more/less? How much will this problem affect the plant?

Are you calibrating your PH pen frequently with a calibrating solution? I had an issue early on with my PH pen but now calibrate it every time and leave it in a calibrating 7.0 solution (as recommend by mfg.)

I've got a Bluelab pen and an American Marine Pinpoint pH meter. I cleaned and calibrated both of them after discovering the sudden drop. They might have been slightly off, but I'm getting the same lowered pH reading (it's up to 5.0 run-off after 2 days of raising it by .5/day), so I don't think it's the meters.

zandramas said:

I've got a Bluelab pen and an American Marine Pinpoint pH meter. I cleaned and calibrated both of them after discovering the sudden drop. They might have been slightly off, but I'm getting the same lowered pH reading (it's up to 5.0 run-off after 2 days of raising it by .5/day), so I don't think it's the meters.

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It's possible the change in light hours is causing your girls to use more/less of a particular nutrient.

Maybe once you put them into flower the bucket you had lowered was too low cause they are wanting different amounts of different nutrients cause it's flower now.

They may be allowing more of a certain nutrient pass through cause it's flower time. Just some thoughts. Much love and good vibes.

Yeah, after searching for awhile I found one other post that said the same thing. I'm going to test run-off samples every couple hours after tonight's watering to see how fast it's dropping. My fear is that the range between what I'm putting in the bucket and the where it stabilizes (I'm guessing it might end up being something like 7.5pH in --> 5.8pH) will somehow not be good for the plant, but I don't think I have any other choice.

+rep and thanks for the input!