Need Advice on PH Runoff Levels

Hello All,

This is my second grow; the first was sketchy but i did manage to make it through to harvest. I learned a lot.

This grow has been a lot smoother but for several weeks now I feel like my soil PH level is on the low side. Yesterday I noticed what I think are signs of a Potassium deficiency so the PH level is back to the forefront of things.

I am in 3 gallon fabric containers with Fox Farms Happy Frog. I water/feed about every 3-4 days using scales to keep tract of their weight and thus moisture content. I feed with 2-3 liters to 20-25% runoff.

This log shows the PH of my feed and the runoff since I transplanted to their final containers. It always comes out lower than the input levels and seems to like staying around 6 or a bit under regardless of the input PH level.

I did try to bump the PH level up using a bit of hyrdrated lime mixed in water to a PH of about 9. After this treatment I didn’t notice any real change in things.

I did a slurry test… after 15 minutes I got a PH of 5.6. Retested after 24 hrs and got 5.9.

Anyone have any thoughts or recommendations?


Sorry I don’t have an answer here. But I am interested in what the team comes up with. Good luck!

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What type of ph tester do you have?pict of plant would help as well.

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Thanks for the reply. Hopefully we can get it sorted out

Thanks for the reply. The PH test pens I use are the cheap ones like the one in this picture. I actually use two of them and average the results. Normally they read within .2 ph of each other. I have calibrated them a time or two this grow and check calibration several times. They seem to be holding calibration well.

I plucked this leaf a few days ago:

This was from about 3 weeks ago:

What i noticed yesterday was a sudden onset of more leaves dying , tips all dried out and curling up and a lot of smallish round brownish/rust color spots spread throughout the dying leaves.

I should have taken some pictures yesterday evening but I went ahead and pruned off the worst of it. They are in night mode until early this afternoon.

Thanks for you help!

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Welcome ! First leaf picture showing nute burn. Follow up with runoff PPM check make adjustments accordingly. Also I recommend apera or blue lab pH digital meter. Both about 50 bucks , If you continue to grow well worth the money. It’s hard to depend on the cheap pH meters. Good luck


Hi Kellydans, thanks for the reply. I probably shouldn’t have posted that first picture. It came from the very bottom of the plant and really doesn’t represent the brownish rust color spots I am really seeing. I will take some pictures this evening.

I do keep tract of the PPM, here is that chart. My runoff PPM is always higher than feed except for the last entry. Please let me know your thoughts on it.

Let’s see an overall shot of plant in white light and fill this out so know a bit about your grow.

COPY/PASTE the below list into your forum post.

Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so; Or post
NA (non applicable)

  • What strain, Seed bank, or bag seed
  • Method: Soil w/salt, Organic soil, Hydroponics, Aquaponics, KNF
  • Vessels: Pots, Grow beds, Buckets, Troths
  • PH of Water, Solution, runoff (if Applicable)
  • PPM/TDS or EC of nutrient solution if applicable
  • Indoor or Outdoor
  • Light system
  • Temps; Day, Night
  • Humidity; Day, Night
  • Ventilation system; Yes, No, Size
  • AC, Humidifier, De-humidifier,
  • Co2; Yes, No

Always try to upload a clear picture of any issues you may have to allow the community to assist you.

Add anything else you feel would help us give you a most informed answer should be included. Feel free to elaborate, but short and to the point questions and facts will help us help you in a more efficient manner :slight_smile:


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I will take some photos in natural lighting this afternoon when my dark cycle ends. Thanks

Requested Information:

What strain: Northern Lights Feminized Seeds

Method: Soil: Fox Farms Happy Frog

Vessels: 3 Gallon Fabric Pots

PH of Water

  • Solution: 6.2-7.6 (see chart in first post for more info)
  • Runoff: 5.4-6.1

PPM/TDS or EC of nutrient solution:

  • 519-859 PPM
  • 1.1-1.8 EC (see 2 posts above for more info)

Indoor or Outdoor: Indoor Grow

Light system:

  • (3) Growstar Full Spectrum LED
  • 115 watt actual current draw each
  • Red(650-660nm, 620-630nm), Orange(600-610nm), Blue(430-440nm, 450-460nm, 460-470nm), UV(380-400nm), IR(740-760nm), White(4000-4500K, 6000-6500K), CREE COB(3000K)
  • LUX at top of canopy= 32,000 (estimated PAR = 820)

Temps: Day: 74-78 deg. F. Night: 74 deg. F.

Humidity: Day: 50-55% RH , Night: Same

Ventilation system: Separate intake and exhaust fans providing 5 air changes per minute roughly

AC: Yes from adjacent room

Humidifier: Yes

De-humidifier: No

Co2: No

Tag me when you put them up?

Hi @Myfriendis410,

Here are the photos you requested. She is about 33" tall and one of three identical strain. She is the only one showing this issue.

I appreciate you help and look forward to your comments.


I see old leaves, somewhat brittle but size of plant tells me it’s time to supplement. The HF is likely depleted.

Thank you, I will start pushing on them with the nutrients and monitor things closely.

First thing I see Happy Frog is very stable you should not have to add any lime or any acidifier it’s buffered already with Happy Frog there’s really no reason to be doing slurry test for ppm’s or pH first sign of a deficiency start feeding more it’s very simple soil it takes all the guesswork and needing to know numbers out of it that’s the beauty of foxfarm

Those Mark’s look like the could be calcium def. Or leaf pests

Thanks for the reply. Being my second grow and after my first being iffy I thought I would take a more scientific approach this time. Besides I like playing with numbers. I am starting to believe the Happy Frog is buffered pretty good. I haven’t got real aggressive at trying to raise the PH level but it seems to like staying right at 6.0 or a little under. I would feel better if it was a touch higher.

Hello @Myfriendis410,

Just following up on my leaf issue. It has been about a week and a half since we talked last. I have increased the nutrients I feed with.

I am not sure my issue is completely solved. The very topmost sugar leaves look great, some fan leaves a little farther down not so good.

Is it possible I have too much light on them? The reason I ask is my third plant looks perfect. But she is 10" shorter than these two problem children so she doesn’t receive as much light. A couple days ago I started raising her up but too soon to see an ill effects yet.

Here are a couple of pictures. What do you think?


That picture shows nute burn.