Noobie grower (been years) screwed up light intensity, help!

Ok, it’s been years, I’m just starting growing again:

Spider farmer SF4000 (430w LED light w/samsung LEDs), and 2x generic 200w Samsung LED side lights.

Well water at PH 6.5 (measured and adjusted) after adding fertilizer of 6,4,4 Foxfarm Growbig

Foxfarm Ocean soil mix

Fresh air continually going into grow room

18/6 light schedule

Day time is around 76 deg, night drops to 65 or so (it’s very cold were I live so my grow tent is a bit colder than I’d like. This is controlled with a spiderfarmer thermostat/duct fan

The plants are now about 5 weeks old and were doing well but I majorly screwed up. Not thinking and not being used to LED lights, I cranked them all up to%100 (24" from top of canopy). After about 2 weeks the plants showed burn spots on leaves closest to the lights and shade spots were fine looking, followed by the top leaves turning a lighter green color. DAMMIT!

When it first happened I thought maybe I was over fertilizing or maybe the soil was ‘hot’ but did some googling and realized my mistake.

So now where I am at now. I dialed the lights back to %60 instead of %100. According to Spiderfarmer this light will do 1135 PPFD @ 22" from the canopy top. So not owing a PAR meter, I got my phone out, loaded the Android PPFD meter app. Then I calibrated (light at %100) to 1135 @ 22" center of the light. Then I adjusted the light until I achieved around 500-600 PPFD around the entire cop of the canopy which ended up around %60 on the light dial. Hopefully this is ballpark okay. After I calibrated the app, I turned the 2 side lights on and using my ‘calibrated’ phone I adjusted all 3 lights until I was 500-600 at the top of the canopy… HOPEFULLY I am understanding this correctly.

Please review my crap and let me know what/where I may be missing something.
Many thanks!!


If it were mine I’d slam the lights down within 8" of the tops and turn them down to 25% or so: this will allow for better canopy penetration to the understory of plants.

I would also do a bit of selective fan leaf removal to increase light and air to interior of plants. This to avoid the dreaded WPM.

Plants look nice; your spotting with high intensity is likely a C deficiency and a dose of Cal Mag in your nutrient regimen might be good. High intensity lights make Cannabis C-hungry.

I would also do a runoff test of media to determine if you should be supplementing now or to wait a bit longer.

As plants approach flower you will want to turn up lights and then crank 'em up when you flip to 12/12 (to make your DLI). Nice setup and plants overall look great.


Okay! That is very helpful. Really 8" or so and really low… interesting. I was thinking that having the lights a bit higher allowed more light penetration but maybe it’s opposite! Cal Mag eh? Im actually not familiar with what that is.

Runoff test, definitely need to give this a check.

As far as select fan leaf removal, I have been removing a lot actually. I’m a bit scared to remove too many, but obviously light and air needs to get into the center of the plants. … I’ll give them a really good check/trimming tonight… what is WPM? I do have outside fresh air vented directly into the grow chamber which is then moved around with a tower oscillating fan. The humidity is around 45-50 in general so, maybe decent?

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Impressive set up you’ve got!

Just how many plants it that canopy encompass?

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Hey thank you! I tried not to cheap out on anything. It’s a Viperspectra Grow tent, which is 5x5x8. Im growing 9 plants in 3 gallon buckets. They are actually Power Plant, Jack Herrer, and White Widow.


White Powdery Mildew: can lead to bud rot

That’s a good place to be.

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Sounds like you got it under control. And yeah since you got the app and know what you’re doing.
You can achieve the par you need by it being high and turned up or low and turned down.
Pros and cons to both some will argue, but I like low a turned down my self, my Roi-e720 (720w at 100%) never gets turned over 75% all the way to harvest


Just wow. :exploding_head: nice

Cal mag is supplement you should have in your quiver it stands for calcium magnesium

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Doesn’t ILGM specify a four week rinse interval? (Cal-mag)

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Not that I’ve seen.

Those are FF specs. My bad.

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Damn, that is a nice setup. The lights alone are impressive. Gonna be following along for this one

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Thanks!! I wanted to make damn sure I had enough light to get into the canopy. The Spiderfarmer SF4000 was like $500 bux, but the 2 side lights were $110 a piece. Some knock off chinese brand, but they seemed to have the correct Samsung LEDs (I did verify the look of them) and a Meanwell LED driver which is a good one. So overall about $720 bux in lights. I think maybe if I did it again, I’d get the Spider Farmer SF7000 just because its got less cables and stuff. Either way, this is nicely flexible.

I REALLY need to grow some balls and just trim these girls but it actually scares me a bit. I certainly have already trimmed off quite a lot of bigger leaves, and also looking down from the top, I do try and clear out big leaves that are blocking bud sites. Still, looking around I feel like I need to do a lot more trimming.

Oh question, It’s absolutely FREEZING where I live. I’m having a hard time keeping my tent above 70 deg F. Is this too cold you guys think?

It was for me i had to wire another circuit into mine for the larger space heaters but it got me up to the 80’s i also keep my humidity around 40,45%. I have been told that plants under Leds like temps alittle hotter ( strain dependent of course) than cmh/hps do I dont know but it improved my girls alot. Happy Growing.

Snatch an oil filled heater for the tent. Stick her in front of 1 of the fans. Prob solved. Running the heater at less than half will make the tent nice and toasty. No moving parts. No extra airflow.

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OK I am in day 50 in budding here, meaning from the light flip 12/12. I am not sure if the White widow here is done. My brain says wait one more week (7) days. There are amber trics on the sugar leaves but not the buds.

Power plant:

White Widow:

Im on eggshells here folks. I’ve never gotten the harvest time quite right.



I dont know much friend but those are some beauties you got there. A little thing I watch for before i even drag out my loupe is that as long as shes throwing quite a few white pistols shes still swelling most of the time. I just wait for about 75% of my pistols to mature then start checking my tricombs. When i see about 10 to 15% amber I set em out in the dark for a couple days kinda let her know the end is near then chop. But thats just my opinion and how I like mine. You may prefer being a more sedated “couch locked” kinda effect if thats the case Id wait till she was about 25/30% amber, i try not to let the thc degrade anymore than that myself. But its kind of a personal preferance I suppose. Peace and Happy Growing to ya. Sorry just seen this was like two weeks ago hope you got sorted out.

Lotsa white hairs. She has more for you. Wait her out couple weeks is what i would do.