Help!! Need opinions

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staysmokin

Member
Hi ive currently got a plant that looks like could be showing signs of some sort of stress. Im running mars hydro fce 6500 bar light with 5g pots of coco loco. I use foxfarm cuktivation nutrients water ph to 5.8-6.2 temps usually 70-72 humidity 55-60% . Cant decide if its light stress or what. i have light at 50% and it is atleast 30" above the tent. The plant shows purplish stems towards the top of plant not so much on bottom. Cant tell if its genetic strain is supposed to bad apple. It looks like could also be a.deficiency maybe im locking something out. Excuse the mess i just finished defoliating and didnt clean up yet before taking the pics. . Any help would be appreciated.
 

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ec121

Well-Known Member
If you want to grow in coco, use unamended coco. Cultivation Nation is 70/30 coco/perlite; Coco Loco is amended with fertilizers, so you need to give it like 3-4 weeks before you start adding bottled nutrients or reamending.
 
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ec121

Well-Known Member
What EC are you feeding at? What is the EC of the runoff? Figure out the answers to those two questions and you'll figure out what the issue likely is and how to rectify it.

Get something like the Photone app for iOS to measure your PPFD so you can get a good enough ballpark and not guess.
 
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staysmokin

Member
ec121 said:
What EC are you feeding at? What is the EC of the runoff? Figure out the answers to those two questions and you'll figure out what the issue likely is and how to rectify it.

Get something like the Photone app for iOS to measure your PPFD so you can get a good enough ballpark and not guess.
Click to expand...
Week 4 veg nutrients half strength input1060ppm @ 700ppm units
Ph-5.9
RUNoff
2130 ppm@700 units
Ph6.2
 
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Delps8

Well-Known Member
They're way under lighted. Your plants are tall and slender with not a lot of branches and leaves. Those are characteristics of plants that are not getting much light. Add in the fact that you're cutting off leaves and your plant is struggling.

At 50% and 30", they're getting seedling levels of light. I don't think that's causing the nutrient issues but it certainly isn't helping the plants grow.

If you were to drop the light to 12", your plants would be getting about 600µmol at the 50% dimmer setting. That's good for early veg.

At only 72°, your plant can't grow very quickly. The temp + RH is good - that's a VPD of 1.0± but at that low a temperature, the metabolic rate of the plant is very low. Lowering the light will help add some heat.

With the increased temperature,

1725071801609.png


This chart is from the infamous Chandra paper and it shows net photosynthesis at various temperatures and CO2 concentrations. It does not indicate yield — that's a completely different issue.

70°F = 21°C and plants at that temperatures have generating about 7µmol/sq meter./second (glucose and O2). When the temperature was raised to 77/25, net photosynthesis doubled. Raising the temperature to 30° (86°F) increase net P to about 17µmol.

Chandra - Cannabis photosynthesis vs PPFD and Temp.png

Since this thread isn't about light, per se, I'll hold off on a deluge of information but will leave a tidbit:

1725072774127.png

Cannab is a light whore loves light and does better at temps up to 85°F or so.
 
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ec121

Well-Known Member
staysmokin said:
Week 4 veg nutrients half strength input1060ppm @ 700ppm units
Ph-5.9
RUNoff
2130 ppm@700 units
Ph6.2
Click to expand...
So you're feeding at 1.5 EC and the runoff is coming out at 3.0 EC. There's your problem. While you need to fix your lighting, that's not what's causing your plant to shit the bed.

Flush with balanced nute solution at 500 ppm (700 scale) until the runoff comes out at 800 ppm (700 scale) and then feed daily at 800 ppm (700 scale) and monitor runoff.
 
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