Help with leaf problem on some plants

I have 10 plants all planted at same time, all from same seed bank same strain. I have water moisture meter all good, use tap water, Ph 7 what could be the problemFluro light 24/7width=“281” height=“500”>


Your PH is way, way out of range. You need a PH Meter and definitely fill out this Support Ticket.


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Strain; Type, Bag seed, or NA Indica

Soil in pots, Hydroponic, or Coco? Potting mix

System type? ?

PH of runoff or solution in reservoir? Soil PH 7

What is strength of nutrient mix? EC, or TDS not using any yet

Indoor or Outdoor

Light system, size? 2 x fluro 50mm off top of plants

Temps; Day, Night 20 dec C

Humidity; Day, Night not sure

Ventilation system; Yes, No, Size just fresh air

AC, Humidifier, De-humidifier, none

Co2; Yes, No No

Thanks, PH is 7 I have moisture meter & PH meter, could it be the lighting?

Your P H is way out of range. Get your PH down at run off to 6.0

There is only one accurate way to adjust the pH. This is using pH test papers or a pH meter. When the pH level is outside the range, the nutrients are less available to the marijuana plant. This means that the roots don’t have access to them and now the plant indicates deficiencies, even though the nutrients may be present. If the pH level is outside the proper pH range, marijuana plants have small dark-green leafs and grow very slowly, when growing in water or soil. Check the pH (by using test strips or a pH meter) before you plant them in soil or planting mix.

To check the pH use collected runoff water. If it’s to alkaline, use soil sulfur to adjust the pH. If it’s too acidic, use lime.

Hope this helps


Thanks Will,

I have a PH meter, the meter shows PH at 7, I also have a kit where I put drops of solution in the sample soil then sprinkle a powder on then match the colour of the power against the card supplied to measure the PH. To get a runoff do I just water the pot until I get it out the base of the pot then use the meter or the kit?

You got it! Do that and test the runoff that will give you the PH at the root and that’s where it counts


A pH of 7 might be a tad high. 6.5 pH is considered ideal for soil.

How do you actually get the measurement of the pH in your soil? If you could give more detail about this powder, I’m not familiar with how that works. Testing the run-off will give you an idea of what is building up in the soil. It will not necesarily tell you exactly what is in the soil. There is a sort of formula that uses the pH value of the water or mixture you pour in the top and then the number you read in the run-off, then you take the 2 numbers and can figure out an estimate for what is actually going on in the root zone.

Hope this helps,


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EC or TDS, you say you are not using any yet. However what is in the potting mix? It could be too “hot” or strong of nutrient concentration for such small plants.

Yes, the actual heat coming off the fluorescent bulbs might be a little high, raising the light another few centimeters would probably help. 50mm is awfully close, that is only about 2 inches for the americans paying attention to this post.

Hope this helps,



Im new, not sure what EC or TDS are, assume nutes.
I will lift the light, I have tested the PH of the tap water is around 9, yet the run off is about 7.
I boiled the tap water & tested the PH, was back to 7, is this a way of controlling these levels?

EC is electrical conductivity and TDS is total dissolved solids in parts per million. Basically it is a way of measuring or estimating the concentration or strength of minerals and/or nutrient salts in your water, nutrient mix or your soil.

Check out this grower’s post, they had some similar questions and are also totally new:


yeah ph m8 6 to 6.5 ,correct it and they will come good ,think the phos cant be taken up when the ph is out causes yellowing of new growth .and like Mac says light a bit close

Thanks MacG :smile: I will do some reading

Please let us know if anything changes. Love to learn for future reference.

I had a similar problem about a year ago and it turns out that my light was too close to the plants, causing all of them to yellow from too much light not from heat, and like everyone suggested, PH is a bit high.

Some of yours look like slight heat stress as well, especially the 2 in the 3rd picture( far left) - leaves seem to want to grow vertical up towards the light rather than horizontal (flat). Some leaves edges seem to be curling upward as well, pretty sure that’s heat, plant is trying to reduce its surface area available to the light to reduce evaporation and not have all that heat beating down on it…could be wrong though so good luck.

2 posts were merged into an existing topic: Purple kush but she’s getting these yellow spots on her what is it

Hello guys, would really appreciate any help on this one
Have a question about pH, i am wondering if it is in the correct range for my 4 girls
I am not seeing any symptoms of distress with them but i feel they could be better
I have that low tech ph meter with the 2 rods sticking out, i tried it on bottled water and figured out that he reads1 unit less then indicated on the bottle and so i adjust my readings accordingly
So i stick it in the soil after i water the plants and it reads 6.7 or so
Lately it is reading around 7.2-7.3
The thing is when i Test the bottle were I dissolve the nutes and from which i water it indicates smthg like 4?! Is that normal?? And if it is why my soil ph is getting higher if am watering with water that has a low ph?

This is a picture of the girls, 2 Sskunk and 2 WW all autos and fem ( opposite corners) under a 400 wats hps
They are 39 days old since germination and put under scrog 7 days ago, currently on 2-1-4 nute formula with micro nutrients

What do you think