2 weeks from finishing and have a problem

[Makeminefullgrown]

Hello, I’m growing 3 clones (fruity pebbles OG, Grandi Guava and white truffle x okie) and just finished up 7 weeks of flowering.
First time growing all 3 and overall it’s went well, except for some sort of issue w/ the White Truffle.
They’ve all gotten the same treatment. You’ll see in the pics there is some burning/yellowing on the tips and all around the edges, with some leaves yellowing in the margins.
Also, the upper section has lightened up with the lower staying darker green.
Initially I thought about light/heat being the cause b/c it’s been crazy hot here (Virginia) and I was pushing them at about 900ppfd…..
I dialed my lights back and raised them a bit…..plus I’ve had to keep the door open just to get my daytime temps into the 77-78f range.
I’ve also considered it could be a K deficiency. The affected leaves certainly present all the symptoms.
Anyhow my grow specs are below and the pics will show both of the other plants that aren’t showing this same issue along with several pics of the problem plant, plus a group shot with the white truffle being in the middle.
Any help is appreciated…..so thanks.
Grow specs:
Medium- Fox farms 70/30 buffered coco
Feed- dry organics
LED Lights- HLG 320 & HLG 150…470W total
Space- 2’x6’ closet with 4” exhaust & passive intake.
I’ve had about a dozen grows with this same setup & recipe and have had very few issues.
Whatta ya think??

 

[zigzagman1960]

Plants under LEDs need temps up around 84f during lights on. Next grow maybe an oil space heater.

 

[BeanTownFan420]

Plants under LEDs need temps up around 84f during lights on. Next grow maybe an oil space heater.

 

[zigzagman1960]

Do a little studying on LST. Here’s a clue—it don’t mean low stress training. Optimal leaf surface temperature for nutrient uptake and photosynthesis is 88f with LED lighting. You will get there with 84f in your tent during lights on.
I see deficiencies in all those plants—keep em green till chop—unless your dealing with purple genetics.

 

[Makeminefullgrown]

Plants under LEDs need temps up around 84f during lights on. Next grow maybe an oil space heater.

I have a heater….and during veg and early flower I kept the lights-on temps up in the 80-82f range. I’ve always lowered lights-on temps by 4-5 degrees F once it gets later into flower.
I was thinking the light intensity may have effected them…..but I’m not sure what has caused it.

 

[Makeminefullgrown]

Do a little studying on LST. Here’s a clue—it don’t mean low stress training. Optimal leaf surface temperature for nutrient uptake and photosynthesis is 88f with LED lighting. You will get there with 84f in your tent during lights on.
I see deficiencies in all those plants—keep em green till chop—unless your dealing with purple genetics.

Thanks for the info…..perhaps i should consider higher temps. I have always thought 80-82f for veg & early flower, then drop it a bit for the last half of flower.
I let my lights off temps get a little low recently and it hence the purple leaves…..
Tell me, if they were your plants, would u raise the daytime temps?

 

[Roy Growin]

Are you giving any supplemental CaMg?
Some strains, mostly indicas, can be greedy buggers so feeding different strains the same nute regime can cause a slight problem depending on their individual genetics
IMO your temps are not an issue

 

[zigzagman1960]

Thanks for the info…..perhaps i should consider higher temps. I have always thought 80-82f for veg & early flower, then drop it a bit for the last half of flower.
I let my lights off temps get a little low recently and it hence the purple leaves…..
Tell me, if they were your plants, would u raise the daytime temps?

google leaf surface temps for cannabis using LEDs—lots of good info out there

 

[zigzagman1960]

I do have to say those buds look awesome. You saying you have two weeks left is an excellent assessment, calyxes look like popped pop corn and 99% of your pistils will be dead and shriveled!

 

[Makeminefullgrown]

Wouldn’t LST be lower than the air temp?
88f LST would require 91-92f air temp

 

[Makeminefullgrown]

I do have to say those buds look awesome. You saying you have two weeks left is an excellent assessment, calyxes look like popped pop corn and 99% of your pistils will be dead and shriveled!

Thanks man….
It’s funny, many years ago, the old timer that taught me how to grow outdoors had a tattoo of the Zigzag man……
The good lord made him an Angel 15 yrs ago…..but maybe it’s fate that I’d get some good advice from another Zigzag man..

 

[zigzagman1960]

Wouldn’t LST be lower than the air temp?
88f LST would require 91-92f air temp

Everything I’ve read says the leaves get 88 with 84 ambient. I haven’t used a temp reader to confirm

 

[SmokingWings]

I dialed my lights back and raised them a bit…..plus I’ve had to keep the door open just to get my daytime temps into the 77-78f range.

If you are thinking about raising the temperature of the leaf canopy as some are mentioning maybe it is time to dial the lights to where they were before. And there is the option of changing the amount that the tent door is open.

Might not need a space heater at all.

 

[The70’s]

I have never read this LST theory, the reading on is is all over ghe place, 72°-86° regardless looks like theres a lot of wiggle room as to temps, i gotta do more reading.

My temps are rarely above 78°, buds are very strong with a good amount of Rosin when i press it. I just pressed some Watermelon Zkittles and i got 2g out of 7g of flower, which is more than the usual 7:1 ratio…… interesting

***read with caution, im only on my 3rd grow***