Yellow and brown dry leaves near the top

I am 70 days in with 36 days of flower with an ILGM Purple Punch. My third grow with the first two great results with the help of this forum.
For this grow I am using city water instead of distilled water. I use a water filter. The ph to 6.0 or within .2 of that.
I have some larger leaves near the top of the plant that are yellow and brown, then crumble to dust when I touch them.
The plant is not getting any taller. Tons of flower though on this plant.
From what I can read and find on the internet it looks like a potassium deficiency. If it is a potassium problem, what would I use to get the potassium up? If it is not potassium, what do you think the problem is? Could the change of water be my problem?
Soil grow using Happy Frog and Pro Mix and using nutes during watering every third day. Light is 18/6 full power 14 inches above the plant. Single plant in my small tent with a fan and TS1000 light, dehumidifier. In the south of the U.S. my temp in the tent is 90 - 92 degrees in the day with the light out. Down to 78 - 80. Humidity is 58 - 65%.
This forum has helped me a ton in the past. Hope you can help me again!

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Pics or it didn’t happen. :slight_smile:

Do you know your runoff pH and PPM? What nutes are you using? Do you know the PPM of your tap water?

5.9 ph in and 4.8 out. I cant get the PPM to work. I am using Fox Farm Micro, Fox Farms Grow Big, CalMag, GAIA Power Bloom and General Purpose.
650PPM in and 240 out. (If these numbers are not within the proper range it is because I believe I am having problems with the meter)


Ditch these 2 and add FF Tiger Bloom. Your current balance of nutrients isn’t want the plant needs and stacking excess nutrients can overwhelm your plant and lead to other things like a mineral salt buildup. I suspect that a salt buildup is the cause of your pH problem. You may need to flush your soil to get things back in line.

This is a problem. Your target runoff is 6.5.


I’ll do the flush and change the nutes. Thanks!

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Way too low

Thanks @MidwestGuy. I have raised the ph from your advise earlier. I used the 5.9 in my post because that is what I was using. However, to get a 6.5 runoff what is the going in ph?

It may take a few waterings to get it back in range. I usually water at a pH of 8.0 over a few waterings to get the job done. Don’t go too high on the input pH all at once or you risk damaging the plant.

Your pH is way out of line, so it will take some time to get it corrected without shocking the plant.

Your plant should do fine when pH and PPM are corrected. Your target runoff PPM is ~1,000, give or take.


@MidwestGuy Thanks. I will start today and see if I can get it down.
The PPM meter is always OR (out of range).
Even though I watered two days ago, should I start the plain watering now and add enough so that I get a runoff to measure? I will start at 6.5 and increase the ph when I water.

I have a heat wave going thru for the next few days. Inside the tent this a.m., temp was 93.4 with a 54% rh. I have installed another fan to send cooler air into the tent from the outside.
I haven’t grown in the main part of the summer yet. My previous grows were Fall and Winter.
I have a little more than 2 months to go, :grimacing:

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I would water with just tap and allow a few runoffs. This could take a few gallons of water. Check your ph of tap going in amd take note. If youve got a ph of 5 and your target it 6.5 you want to water with at least a ph of 7 to 7.5 going in. Make sure afyer you reach your target ph with runoff to also check ppm of your final. If below 1000, take that ppm and feed the appropriate ppm remember to check ph after you add nutes and then feed. Dont freak out if the plant shocks a bit.

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Alright, I will get started shortly. And I will give updates.

For reference, what does a shock to the plant look like?

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Drooping leaves, changing color, stunted growth, anything outside the norm.

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I just put in over 3 hours getting the numbers down to the recommended levels. 10 gallons of water (38 liters) and now all seems good by the numbers, I think.
Started with:

6.5 5.0 580 5240 !
6.5 5.7 580 2820
6.8 5.8 560 2270
6.8 5.8 560 1980
6.8 6.2 580 1520
6.8 6.5 580 1490
7.3 CHNG 6.2 540 1650 Tried a higher ph
6.8 6.3 580 1250
6.8 6.4 580 1100
6.8 6.6 570 1020

I stopped there. Since I was watering at 5.8ph before I was advised to go to 7.8 - 8.0, I went up one point to do the flush. When I water in 3 or 4 days, I will step the ph up to 7.2. I am trying not to shock the plant too much. Each 3 to 4 days that I water, I will raise the ph.

40 days in flower. The buds look great but the leaves were yellow/brown and crispy.

I had the info all spaced out and and organized. Now it posts all crunched up…

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+1 on using Tiger Bloom. It has NEVER failed me. But don’t overuse, and mix (dilute) per the instructions on bottle.

@Me75 stop right where youre at. Numbers are perfect. In flower 6.8 is the sweet spot for me if im checking ph. The nutients thay she will need during flower are more easily absorbed at 6.8ph.

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Alright!! Thanks for the help.

Just so you are aware as to why, synthetic fertilizers leave behind salts and these salts must be washed away on a routine or they built up causing issues like you see now. Ph crashes/fluctuations, severe burning when medium dries out.

Fixing the problem is great and so it knowing why and how it happened.

Your runoff parameters look great! She will be back on track!

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Doesn’t look much better!

I had a little yellowing on the leaves of this Purple Punch. After some suggestion I ended up flushing the plant. Numbers are above. On the next watering 5 days later, I put in some grow and bloom nutes. Half as much as before. Now I ended up with this. The PPM out has risen from 1050 to 1330 today.
Soil grow, water is from the garden hose thru a chlorine filter then the water
sat for 2 days until I did the ph. Using 6.8 as the ph number. All measuring tools have been calibrated.
What’s up please?