Lighting Is this light burn?

[Misanthrope82]

Hello, everyone. I have a problem here. I've had some plants outdoors for about 6 weeks with no issues whatsoever. I recently acquired a new light and tent (1200w cob and a 3 x 3 tent) and moved the plants inside.

I already had a feeling this light was too powerful for my grow space and the hangers it came with were garbage and I wasn't able to raise it as high as I would have liked to.

I checked on the plants after about 24 hours and noticed these marks on quite a few leaves. They looked fine until I moved them in the tent under the light. Naturally, I panicked and moved them back outside. When I checked on them this morning, it seemed to have gotten worse. The leaves were still wet from the morning dew and I noticed when I rubbed these marks, it left a brownish residue on my fingers! Here is the light that I purchased for my 3 x 3 space:

http://www.hipargero.com/product/ledgrowlight/

Are these marks burning as a result of the light? That's my only assumption as they were fine before I put them under it.

I included 3 photos. Thanks, everyone.

 

[Animatey]

Does not look like light burn to me.

Light burn would more likely affect the top most leaves before the rest of the plant. Also when plants go under real intense light when they aren't ready for it, they droop real hard.

Looks like possible calcium deficiency, but I'm not 100% sure. I'd personally try to troubleshoot it like a root zone/nutrient issue. How's the pH of your feed/soil?

I've never grown in soil, so maybe someone with soil experience can help clarify, but doesn't look like a lighting issue at all to me.

350 watts of cob is about right in a 3x3. You'd probably want it 18 inches above your plants, or as low as 12 once they got used to it, but check with the manufacturer to be sure.

 

[Misanthrope82]

Most of the leaves affected were the upper ones, with some leaves in the middle being affected. It was about 18 inches from the top of my plants.

The soil I use is ocean forest which is supposedly pH'd to 6.3 - 6.8. My tap water is just under 7. I use general organics fertilizer which says pHing nutrient mix is not necessary. The plants were fine until I put them in the tent under the light for 24 hours.

I'm pretty stumped. Even though my tent is 3 x 3, the manufacturer recommends it for a 4 x 4 but I didn't put much thought into it.

Supposedly this light matches the power of a 600 watt hps.

 

[Arthur]

Cal/mg.
Led can cause an increase in demand for cal/mg.
That being said, is known for poor QC as of late. I had bags pH in the high 5s before I gave up on them. A low pH would also lock calcium and magnesium, so the cause of the issue still needs to be found.
A slurry test of the medium will get you the info you need. Once you know your "in pot" pH, we can see of it is either lock out or just deficient.

 

[Animatey]

I think if you are growing with those nutes you are right, pHing the feed might not be necessary.

If you look at images of "cannabis calcium deficiency", the images look pretty close to what you've got. Salt buildup or pH issues can cause lockout of micro nutrients like Ca, but with those nutrients I sorta doubt both of those.

Third possibility is that the plants are legit hungry for more Ca and the LED exacerbated the issue.

Not sure... Maybe @Waira can chime in?

Sent from my Moto G (5) Plus using Tapatalk

 

[Misanthrope82]

Thanks, Arthur. It's a starting point.

Forgive me, but how do I conduct a slurry test? And can I do this with the liquid test vial method? I hate digital pH meters.

 

[Misanthrope82]

Yes, Animatey, the pictures look VERY similar when I compared them.

I had know idea LED could starve the plants for more cal mag.

 

[Arthur]

Thanks, Arthur. It's a starting point.

Forgive me, but how do I conduct a slurry test? And can I do this with the liquid test vial method? I hate digital pH meters.

No, a digital meter is required. Honestly it should be one of your first things to get. PH "perfect " nutes can have issues if your water is not in the normal range, while nice to not have to check pH, if your not verifying, when issues arise, your just guessing as to the cause. A "for instance" if your feed is at 6.5 but the soil has slid to 5.9, that puts you somewhere in the low 6s in the root zone.
Here's a copy of the chart I use.

 

[Misanthrope82]

Thanks for the info. I haven't had much luck with digital meters. I always get readings all over the damn place, even when calibrated. Can you recommend a decent one?

 

[Arthur]

Thanks for the info. I haven't had much luck with digital meters. I always get readings all over the damn place, even when calibrated. Can you recommend a decent one?

I'd love to own a bluelabs meter... but $$$. I've been thru countless of the yellow pens, I bought this one last time, so far 8 months and no issues. Was around 40$.