HELP! Browning Leaves in Early Flowering

[Rik]

I’m afraid I’m going to lose this grow. Today is day 75, and 18 days after I flipped to 12/12. She is a Northern Lights photoperiod from Sensi Seeds, planted in FFOF soil and given Fox Farms nutes.

I’ve been struggling with browning leaves the whole grow. It took me weeks to get the runoff pH up to 6.5, as the soil had an extremely low pH at first. Thanks a lot, Fox Farms. I think this may be my last grow with them. Anyway, I finally got the pH up to 6.6, and now it’s coming out at around 6.8. I’m feeding nutes every other watering. Everything is going in at 6.55.

Now I’ve got browning leaves again, and since she’s flowering and won’t be growing new fan leaves, I’m afraid of losing this grow before I can harvest anything. To me it looks like a calcium deficiency but I’m giving her calmag and the pH doesn’t stop calcium uptake so I’m confused. I know it doesn’t look super bad now, but I’m afraid if I don’t fix it immediately that it’ll progress until the whole thing is a goner. Can anybody offer any advice?

Full grow details:

Northern Lights photoperiod from Sensi Seeds
Day 75 from seed sprout
Day 18 since flip to 12/12
Mainlining training
5 gallon fabric pot
FFOF soil
Fox Farm dirty dozen nutes plus calmag
Nutes given every other feeding
Current runoff pH 6.8
Apera Instruments AI311 Premium Series PH60 pH tester pen, calibrated at start of grow
Black Dog LED PhytoMAX-2 600, 615 watts from the wall
Light distance 24” from highest peak of canopy
Temps mid/low 80s during day, low 70s at night
Humidity low 40s during day, mid 50s at night

[Blowdout2269]

Don't panic yet Rik! Good to be concerned though.
If your giving CaMg, and you assume that the pH is correct; have you double checked the calibration of the pen?
I myself have previously had what I believed to be the start of a phosphorus deficiency that looked similar to this shortly into flower.

[OldManGrower]

Good thinking! Problems don't go away on their own and pro active is the only approach to take. I believe you need to add more cal-mag for the spots and MAY be slightly overwatering. Its a nice plant and could greatly benefit from some defoliation. Some of the damage is a result of your PH struggles (been there and done that). I usually keep my PH at 6.7-6.8. I also agree with Blowdout2269 about the pen. It never hurts to make sure that it is properly calibrated.

[Rik]

Thanks for the advice guys. I calibrated again today but it was in good calibration already. Today was a plain watering day but I added an extra strength dose of calmag. Hope it makes a difference. The pH came out at 6.57 so that’s positive.

[KOSTIS]

I assume that you are going to make it to harvest ..! Make your life easier and try AN nutes!