Nutrients off in flower

@Myfriendis410 @dbrn32, one of my plants is yellowing quickly. I believe it started between the veins and has spread. Watered w 3 gallons each of plain ph water 3 days ago. Runoff was 1800 at first, and final runoff was in the 900s.

Appreciate any advice.

–What strain: ILGM Mango Kush photo
-Age of plant: 99 days
-Method: Happy Frog soil w/ GH Trio and CalMag
-Vessels: 5 gal fabric
-PH and TDS of Water, Solution, runoff:
IN: PH 6.4; OUT: PH 6.0, TDS: 990
-Method used to measure PH and TDS: digital handheld meters
-Indoor or Outdoor if indoor, size of grow space: Indoor 4x4 AC Infinity
-Light system brand and wattage/spectrum: ACI Ionboard S44 400W full spectrum
-Actual wattage draw of lights: currently set to 90%
-Current Light Schedule: 12/12
-Temps; Day, Night: Day: 83, Night: 70
-Humidity; Day, Night: Day: 55% Night: 65%
-Ventilation system: 6” inline Cloudline S6, 2 8” fans
-AC, Humidifier, De-humidifier: Humidifier and Dehumidifier available. Not using dehumidifier bc increases temps at night.
-Co2: No


Youre locking out. Your ph needs to be 6.5 to 6.8 for flower. Id go in at 7.5 ph in


Thank you for the quick reply @ChittyChittyBangin. If I was watering normally, I would wait another day or two. Do you think I should/can water today to start to remedy?

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You can. I wouldnt water till 20% runoff though. Just soak the medium and let it sit.

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Done. Thanks again so much. I’ll adjust my PH to 6.5-6.8 moving forward. What type of PH out numbers do you look for in flower @ChittyChittyBangin ?

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I grow organic so i dont check ph or ppms unless i start see issues, then its slurry test time or probe time. Ph out in flower is between 6.8 amd 6.5

Right on. I expect I’ll try organic at some point, but there’s so much to learn! Having this community to lean on is EVERYTHING! :green_heart:


I got a soil probe tester and the PH is still reading in low 4s at the bottom of the pot. A lot of videos I’m watching are suggesting a heavy flush. Your thoughts? Do you know any synthetic nutrient growers on here you could tag for more opinions?

Only necessary if runoff pH is out of line or if PPM is far too high. It is usually necessary due to synthetic nutrient salt buildup over time that submarines root zone pH. With most good cannabis soils a good flush down to a runoff PPM of ~350 will return runoff pH to ~6.5.

Some synthetic nute products are worse than others. Flushes are rarely necessary when using Jacks 321 and a couple of flushes are mandatory if using the FF Trio, which is a very salty product.

Be cautious of what you see on YouTube. There are some good channels out there but keep in mind that the content creators get paid to push out content and some of them will publish anything they think will get clicks whether it is good advice or not.

I would get a good digital tester. The pronged meters are notoriously inaccurate. I have a had time believing that a pH in the low 4s can exist. It’s possible I suppose, but I can’t recall ever seeing a pH that low in the 4 years I have been reading posts here. Bluelab and Apera both make quality meters.

I’m not familiar with GH nutes, but it isn’t a nute line that we commonly see pH issues with IIRC. The FF Trio is the worst by far.


I would not try to flush with a high ph to offset the out ph. I would recommend staying at 6.8 for a while. Going above the 6.8 will only introduce more problems. Now you would be feeding above the soil ph range which is not right thing to do.

Do you know your ppfd?

Thanks @Poseidon1
Assuming I’m using the Photone app correctly, I’m at 625 average ppfd. I took 5 readings from center and each corner edge of the plants at canopy height.

800 is an optimal minimum.

I raised the lights when I started to notice the yellowing some days ago. With that said, any time throughout the grow that I’ve tried to get the PPFD up to recommended values, the plants have seemed stressed to me (leaves brittle and/or twisting. Could there be another environmental factor at play with this?

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Your RH, temps, and airflow are fine. Dunno. 800 PPFD is generally well tolerated. I run my plants at 1,100 PPFD and have never had problems. AC Infinity makes good lights. I’m not sure the light is the problem.

The only other suggestion I have is to get that runoff pH up a bit to ~6.5.


This is what I got. Is this junk?

Yes. None of the pronged meters are accurate.


Careful with ppfd but i believe you need more. I have had light burn at 1050 ppfd, some plants are different, environments as well, which would determine how much they can take. Ive noticed in coco, (for me) i can run a higher ppfd with no ill effects. Gradual changes as well, dont go up alot at once. I shoot for 950 ppfd at center of plant typically.


If i had to guess by pictures I would say plants aren’t being fed enough or often enough.

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Your numbers actually look pretty good, 1800 runoff tds tho in soil is a little high imo but not bad. Are the numbers similar in your other plant? Have you followed the light space recommended by aci? Overdoing calmag can block other nutrients as well. I would focus on getting that ph out up a bit and keep a eye on your runoff tds to see how much there eating.

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