Light stress?

[Burlapin]

not really sure what the issue is here. i was thinking maybe light stress, anyone have ideas?
HLG 550 knock off at 20 inches
3 DWC 5 Gal buckets
around 1000 ppm my meter is malfunctioning right now so i cant be sure.
Humidity is 39% or so and temp is low 70's
PH i let drift from a bout 5.5 to 6.3

 

[Burlapin]

Here are 2 more pics close up to some of the leaf damage

 

[Cantharellus]

That looks like it may be too much light. I have one of those lights on the way so no experience with them yet. I would either raise the light a little or use the dimmer a little. Is this your first run with led ?

 

[Burlapin]

i ran the same light last grow and one of my plants seemed to have a similar issues, i was using coco then. the reason i was thinking light stress was because it seems to mostly be in the center of the tent under the light but i have no idea

 

[Cmoon]

I recently had simular issues being new to Led I had the light 12 in and they liked it a lot better at 24..good luck

 

[Burlapin]

i actually measured again and the light is 23 inches above the leaves showing symptoms it was 20 inch to the tall cola's around the front

 

[GOT_BUD?]

Lights are too close.

Back them off to about 30 inches, see if they improve.

Plants seem to use LED light more efficiently than HPS. Meaning they need less of it to achieve or exceed the same goal.

Right now I have my HLG 600 panel about 36" above my plants in my tent, and am worried I'm going to run out of height when I flip to 12/12.

 

[Grapefruitroop]

I agree with DOC! back the lights and see...
Im in the same situation...600w led at 36 inches and few buds sitting right at the center of the foot print are def receiving too much light...
same browning of the leaf....the bud is developing not bad doh, still very resiny but has a split head and is consistently smaller than the surrounding ....

I reached the roof as far as hanging distance so next I'm gonna come up with probably shorter containers and scrog em better...

today I taught about sticking one of this right on that bud

 

[Cantharellus]

I am no expert but wouldn't it be better to dial the light back a bit so it can stay closer to the canopy ? Wouldn't this give you better penetration and the lights will be more efficient ?

 

[Grapefruitroop]

...maybe, but would that affect the footprint?
and....can you dim any led fixture as much as you want and whenever you want without creating problem to it? im no expert either...

But im thinking that would be wiser building a fixture just to be able to spread the diodes as much as possible....in strips more than put the all tighter in a bunch creating a "hotspot" of insanity...

 

[Shmavis]

not really sure what the issue is here. i was thinking maybe light stress, anyone have ideas?
HLG 550 knock off at 20 inches
3 DWC 5 Gal buckets
around 1000 ppm my meter is malfunctioning right now so i cant be sure.
Humidity is 39% or so and temp is low 70's
PH i let drift from a bout 5.5 to 6.3

[URL=https://www.icmag.com/ic/picture.php?albumid=82061&pictureid=2001368&thumb=1]View Image[/url] [URL=https://www.icmag.com/ic/picture.php?albumid=82061&pictureid=2001367&thumb=1]View Image[/url] [URL=https://www.icmag.com/ic/picture.php?albumid=82061&pictureid=2001366&thumb=1]View Image[/url]

I agree with others about proximity/intensity of the light.

I am still cutting my teeth when it comes to LED so take this for what it's worth - but another thing I have been noticing is that under these high intensity LED panels plants prefer much higher temps and humidity. I haven't found this to be the case under burple panels.

Even under HID I wouldn't run temps that low unless it was a week or two from harvest. And judging by the size of your flowers, I wouldn't be running relative humidity that low, just yet.

You can buy a (relatively) inexpensive PAR meter (Apogee SQ-120) to hook to a multimeter and use PAR readings as your guide instead of distance. I haven't had a lot of luck under my 550 V2 so forked over the cash for the meter to see if I can improve by measuring PPFD instead of going by feel.

 

[Burlapin]

ill back off the light another few inches. the temp on the other hand im gonna have a hard time bringing up until it warms up a bit outside, same with humidity. inside my house humidity is 27%, ill try hang a wet towel and a fan tonight when the lights are on get the humidity closer to 45%ish. i was considering getting a humidifier but because of the exhaust of my two tents in the same room i thought it might be a waste.

 

[Burlapin]

...maybe, but would that affect the footprint?
and....can you dim any led fixture as much as you want and whenever you want without creating problem to it? im no expert either...

But im thinking that would be wiser building a fixture just to be able to spread the diodes as much as possible....in strips more than put the all tighter in a bunch creating a "hotspot" of insanity...

the second led i got, the one for my veg tent,splits into 4 strips and i really like it. in hind sight i would have probably got a similar design for my flower light .

 

[Creeperpark]

When I use high wattage LEDs I had to add more calcium supplement to prevent light burn to the leaves. Under HPS and Sunlight the same plants didn't have burn and and used less calcium.

 

[Creeperpark]

ROLES OF CALCIUM IN PLANTS
CALCIUM promotes proper plant cell elongation. Strengthen cell wall structure - calcium is an essential part of plant cell wall. It forms calcium pectate compounds which give stability to cell walls and bind cells together. Participates in enzymatic and hormonal process's. In lay-man terms it's the bones in the plant cell. LEDs will damage cell walls when the cell is lacking enough CALCIUM to give the cell "Bones so to speak". Extra Calcium is a must when using high wattage LEDs.

 

[Creeperpark]

I found this out when I started a water only fade on 12 cuttings. I had some large Ganish Cuttings under LEDs in one area, and a few others under HPS, and two outside in full Sun. I only got leaf burn on the plants under the LEDs.
After finding this out, I flowered a cutting and held on to the Cal-mag and dropped the nutrients with the fade and No Light Burn!

 

[Creeperpark]

Photos of research

Photos of research

All of these cuttings were from the same Mother and had the same soil mix and exact feedings. The only thing different were the different lighting sources.

 

[Creeperpark]

Even though there are big differences in LEDs and Laser Diodes, they have some similarities too. Available Wavelength difference between LED is 0.66 to 1.65 mm and laser has 0.78 to 1.65 mm.. LEDs generally classified into three wavelengths: ultraviolet, visible, and infrared and Laser are classified in harmful lighting intensity classed 1 through 4! LEDs dispense light with beams the same a Lasers and will burn plant tissue if the plants lack healthy cell development.

 

[Burlapin]

thanks for the info i did a res change last night added some calmag and ive backed my lights off. fingers crossed! thanks everyone for the suggestions

 

[Douglas.Curtis]

Even though there are big differences in LEDs and Laser Diodes, they have some similarities too.

Actually huge differences in output between an LED and a Laser. Lasers can be built to operate in a wide (relatively speaking) range of frequencies.

Though bright, LEDs do not produce 'coherent' light. This is light were every photon is the same frequency, the same energy level, and they're all traveling in the same direction. It's like getting hit with a firehose instead of a sprinkler.

Yes, LEDs can be very, very bright. Their output is still sprinkler style.