Help identify: Light brown spots, leaves light green

Asked this in another forum and got crickets. Hoping for some insight – really bumming me out.

What type of medium; soil or hydro? SOIL
What brand and type of soil? SUNSHINE MIX #4
Indoors or outdoors? INDOORS
What strain? 2 SATIVA, 1 INDICA
How old are the plants? GOT THEM AT 3-4 NODE CLONES, NOW 2.5 WEEKS IN
What type of lights and how many watts? MARS TS-1000
How far from the lights? 36”, was 48” UP UNTIL YESTERDAY
What is your watering frequency and source of water? DISTILLED, EVERY OTHER DAY
What, how much and when was it fed? NPK? 2x SUPER THRIVE PER MANAFAC RECOMMENDATION.
What is the medium/runoff pH and PPM if in hydro?
What are the temps and humidity in the room? 62-73 degrees night/day. 35-40% RELATIVE HUMIDITY
What size pots? 7 GAL
Any other pertinent info?

Light was pretty far from canopy for most of grow. No nutrients added aside from super thrive. Water lightly three days in a row once. Thinking it might be calcium deficiency. Never added lime. PH soil testing said it was right around 7, maybe a little higher. Also, the indica plant seems to be barely growing after two weeks.

Any knowledge or hypotheses about what’s causing the brown spots, yellowing and light green coloration would be helpful.

I think I see your problem it’s the distilled water , your medium is probably naturally higher ph then recommended and you not putting in ph ed water with solids in it is most likely causing lockout

@urge welcome to the neighborhood, I’m seeing a possible nitrogen deficiency but it could be from overwatering or lack of mineral in the distilled water which can cause lockout check out the pics on this link under nitrogen

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oh, i was unaware the distilled water was an issue. i actually have some ph down en route.

should i just add that to my tap water, which is about 7.5?

I know that there are different ways to use distilled or RO water but I always used tap water and adj the ph so I don’t know the trick of using the others. I grow organic living soil and don’t ph anything anymore. Before I switched tho I used tap

Yea and it’s a lot cheaper to use tap water itll take you about 10 drops of GH ph down per gallon to be in acceptable ranges but I recommend getting a ph meter

Once you start feeding the nutes will make your ph drop and you will probably have to use up to adj your mix

OK, i can table the water issue for now as it seems like a solid lead.

still want to figure out: 1) my light height was almost 2x distance recommended. could that have caused or compounded what i’m seeing?

  1. should i add some fish and guano to add nitrogen? the super thrive has a little nitrogen, but unsure about what else. this is fresh soil with 0 grows in it.

  2. if the problem is resolved via the above, how long should i expect to wait until the plant turns it around?

thanks all! really appreciate the info. it’s relieving to just have some possible solutions.

1: in an indirect way the light probably did cause this , with a more appropriate amount of par your girls starting using more nutes causing the sudden deficiencies
2 I’d add a little extra nitrogen but don’t go hog wild those nutes take 2 weeks to fully break down I’d do 3 Tablespoons max per pot until I see recovery(I personally prefer bloodmeal for N)
3 1-2 weeks but the dark spots probably will never go away since that’s necrosis(itll probably get slightly worse before better)

Your stems are also very dark which could be a mag deficiency that again is probably part of the lockout. Just wanted to point out the stems if no one noticed em

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@urge welcome to a brilliant forum. Like @MeEasy said your stems are red which is usually a calmag issue. Your pH is a little off which won’t be helping you either. Try a foliar spray with calmag. I have a plant like that just now and she is responding well to a nightly calmag mist.


Well dang, wish I had more problems for y’all to fix.

Thanks for the much-needed help. Here’s what ima do:

  1. add nitrogen (but not too much)
  2. foliate w calmag w the lights off/out
  3. update watering schedule (less frequent, more water) and change water to a distilled/tap hybrid

Let me know if I’m missing anything. Thanks again. I’ll pay it forward!


Amazing forum @urge. If youre looking for someone sticking @ in front of their user name will bring them along for a chat.

@Davyg @MeEasy @GreenSnek

hey guyyyyys,

so i did the following:

  • added 2 ounces of fish and guano into one gallon of distilled + degassed tap (75%:25%). should be through the gallon in a couple more feedings
  • added 1 tsp of cal mag into the gallon
  • added some tomato trellising
  • gradually lowered light height to 30"

the plants have taken off like never before. hooray! thanks for all your help.

one question, i guess. should i address any other nutrient deficiencies? if they were starved for nitrogen and cal/mag, and they’ve received no supplemental nutrients other than these two, perhaps i should add some potassium and phosphorous?

would love to avoid nutrient issues before they arise from here on out. i’m also going to top and LST in a week or so, or whenever they look healthy enough again.

thanks again. you guys are saints.

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Woo hoo, sounds like your babies are starting to pick up :heart_eyes:. Keep an eye on your new growth from now on and monitor your old growth. I’ve used high sulphate of potash before and it gives me the fear as it’s so strong. Potassium and Phosphorus will be needed in higher quantities as you go in to flower so be careful how you use them. Tomato feed is another good feed but tends to have a low pH so a pH up would be needed, I use baking/bicarbonate soda as a pH up as it’s cheap and readily available :sunglasses: