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Heat stress or something else?


New Member
Greetings 420Mag Forums.

Just wondering if someone with far more experience than I (Which is practically anyone as this is my first grow) could give these pics a quick gander and let me know if I'm looking at heat stress or something else.

Grow info :

This is day 22 from seed (germinated April 28, "sprouted" out of their Rapid Rooters on the 2nd of May)

Coco Coir / Perlite 70/30 mix in 3 gallon fabric pots
Feeding daily with House and Garden Cocos nutes, as per their nutrient calculator, not using a nitrogen booster though ( >> Nutrient Calculator ) and some added Cal/Mag (7.5ml / 6L - the water is already quite high in Calcium, not sure if I should be adding more or not) - Have been mixing with 6L of water per batch, but that's about to go up to 9L.

This particular plant has been getting 2L daily which gives between 25% and 30% runoff. Water is 350ppm tap water (hardly ideal, I know) pHed to 5.7 after nutrients, but before additives (H&G instructions). Runoff tests at around 6.4

Strain is Dark Angel from CropKing Seeds, it's sharing space with two White Widows in a 6'x4' grow tent that has 2 oscillating air circulation fans and 1 460cfm exhaust fan (sucking through a carbon filter first). All 3 plants are under a 1000w MH lamp. (a bit much for this grow, I know, but the website I ordered from screwed up and sent me a 1000w ballast instead of the 600w I ordered, and it was easier to just buy some 1000w bulbs and roll with it). The light is currently a bit over 3 feet above the canopy. It can be raised another 4-6 inches, max.

Noticed this weird leaf discoloration last night, the new growth was a bit yellow as well, but that seems to have gone away. Some of the leaves are ever so slightly cupped upwards as well.

I'm thinking it's heat stress, as we just had a bit of a heat wave and the tent interior was up to 96f with 30-40% humidity, but there may be a nutrient issue as well, so I thought I'd ask for some expert input.



Well-Known Member
Perfectly normal as plants get to sexual maturity. Hormones start changing as she becomes a lady. New growth being a lighter green/yellow is just a sign that shes "coming of age". Some strains do it far more and some less. Usually somewhere around 3-4 weeks old for auto's and 3.5-4.5 weeks old for photos in my experience.
Looks great!

Not sure why you added perlite to coco but you may want to start feeding twice a day soon. Even without added perlite you could feed in coco twice a day. With perlite I would.


New Member
Cool, thanks for the reply!

So, if I feed them twice a day, should I still use a full strength nute regimen or should I cut it in half? Between the coco, the perlite, and the fabric pots, I'm not at all worried about over-watering them, but I don't want to end up with nutrient burn (not really sure how that'll work considering the new stuff would flush out the old).

As for the perlite, I wasn't going to add it at first. Before the grow I researched the crap out of...well, everything, and perlite in coco seems like it's split more or less down the middle of people who use it vs those who don't, but the consensus is that it isn't required.
That said, I started the 3 plants in red solo cups and noticed that the coco basically turned to "mud" and compacted down a lot after feedings, so I mixed some perlite in for my transplants.

I don't know if it's actually helping or not, but the coco doesn't seem to be doing that compact mud thing anymore.
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