I am getting yellowing leaves and my runoff is 7.3 Ph

  1. Indoor or outdoor? - size of grow? Indoor, 4x4 tent

  2. ILGM Grandaddy purp

  3. Feminized seeds

  4. Origin of water. PH, EC/TDS of source water? Tap water, I Ph it to 6.5 and the TDS is about 20 after that

  5. PH and TDS/EC of if mixed solution? I will have to mix some and come back to edit this

  6. Grow method? Soil, Soil-less, Coco, Hydro, Aquaponics. Please explain. Fabric pots, mix of 7+5 gal. about 2/3 fox farm happy frog and 1/3 bushdoctor coco

  7. Nutrients or fertilizer system used. Fox Farm trio at 1/2 strength, plus Cal-mag

  8. What typr of lighting are you using? LED, HID (MH, CMH, HPS), or Fluorescents? Please elaborate. Two full spectrum LED lights. [VIPARSPECTRA P2000 LED Grow Light 4x2ft Coverage Full Spectrum LED]

  9. What are the temps in your growspce? Day / Night? Day 76 F, night 70 F

  10. What is the RH = relative humidity in your growspace? Day / Night? it stays around 50%

  11. AC, Humidifier, De-humidifier? I’m in the house so it’s climate controlled, but it does get a little warmer in the room in the daytime. I ran a humidifier for a while but it hardly ever needed to run so I stopped using it.

  12. Do you have a Ventilation system? Size? 4", 6"? 6" filtered inline fan venting the tent, passave intakes

  13. Co2 Yes / No? No added Co2

  14. How long have you been growing? First time grower!

  15. What budget have you set in order to grow successfully? I haven’t really, I’m trying to keep the recurring costs low and my equipment budget oriented but reasonable.

  16. If you grow hydro, then please explain your hydro method. DWC, R-DWC, Ebb and Flow, Or; Other? Other? Nope

16b. Size and temperature of solution in reservoir?

My plants have been having yellowing and burnt spots on leaves, and it’s only week 4 of flower. It seems to early to be simple fading, I checked my runoff and it was around Ph 7.4 so I decided to flush.
I have put 25 gallons of water through one poor plant and the runoff is still around 7.13. I started feeding it 6.0 water and ended feeding it 4.0 but it all seemed to have almost zero effect on runoff PH. Do I just have a ton of salt buildup in the root zone or what could be causing this? I’m worried my plants are getting sick and I would be devastated to lose them, my jars need filling!
I did about five gallons of the flush with Sledgehammer added to the water, once again seemed to have no effect.


My runoff from the plant I flushed is 469 with input water I think around 400, by the end I was using straight water with pH down to get it to 4.0

Plant is hungry!

How much Calmag are you feeding? Calcium looks fine but magnesium looks low (which is pretty normal with fox farms trio). I would start mixing some plain epsom salt in on water only days. About 1/2 tsp per gallon.


thanks for the reply, do you think that is what is causing the high Ph runoff? My runoff should be in the 6.5 range I thought.
If I feed them will the plants even be able to uptake the nutes with the Ph at 7.1-7.6?

I am feeding them about 3 Ml of botanicare Calmag plus per gallon. Which is the low end of their recomended range. I have been giving them the Cal-mag even on the plain water days though because I think I heard somewhere its ok

Fox farms has always seemed fine on calcium. It’s a magnesium deficiency that usually takes over a plant on fox farms trio. Epsom salt will give them the magnesium that they need.

I’ll go get some epsom salt right now. Do you think the FF trio is okay at 1/2 strength or should I go lower? Or higher? I had some yellowing once during veg but a sledgehammer flush took care of it.

Do you know what your runoff ppm is?

couple of things, you claim your tap water is 20 ppm. if that’s the case i wouldn’t trust your ph reading.

then your runoff is 7.3.

to me this means your soil Ph could be creeping up.

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Are you using lime or some type of soil pH buffer?

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Was scrolling to post this. Depending on how you’re testing ph this could be a factor.


Welcome overall plants look good, If not already verify your ph meter in the fresh bottle of 7 PH solution. What brand meter are you using ?

Yep hit my max posts

PPM of runoff and incoming water:

On the one plant I tried to flush it is 469. That is with about 20-100 going in from just pH water.

On the plant next to it I didn’t flush it is 2112 with 525 going in. That’s the nutrient mix, I added the epsom already at 1/2 tsp per gallon.

I forgot to mention, I am adding a couple tablespoons of unsulfered molasses to each 5 gal bucket I mix for feeding.

For Ph reading I am using one of those basic unbranded amazon ph pens

I calibrated it when I got it with the 3 solutions and it seems to be accurate, but I was messing with it last night and ruined the calibration, next Monday is the quickest I could get new packets to calibrate it. So for now I am using the chemical test that came with my General Hydro Ph up and down.

I am not using any type of soil Ph buffer that I know of, I just bought FF happy frog and mixed in some bushdoctor coco to help with drainage.

couple of things, you claim your tap water is 20 ppm. if that’s the case i wouldn’t trust your ph reading.

then your runoff is 7.3.

to me this means your soil Ph could be creeping up.

Can you please explain this, are Ph readings unreliable when the PPM is very low? I usually add some cal-mag or at least molasses so that should bring the PPM up but I’ve never checked it

Correct you need at least 100ppm preferably above 150ppm to get an accurate PH reading

It seems like the epsom salts did the trick thanks.
And the knowledge about pH and ppm will be very helpful also!