Plants having burned leaves

My plants are having burned leaves and I'm not sure what exactly is the cause of this so i figured maybe you guys can help!

I have 9 plants and 5 of them doesn't have any burned leaves while the other 4 does. I'm using HLG 650r LED. They are all in the same tent and here are some info on the conditions:

• Temperature 21-23c lights off and around 26-28c lights on.
• PPFD around 650 - 750 and the light is around 88 cm away from the plants (34-35 inches). I am on the 9th day of flowering (after a month of veg)
• Using biobizz nutrients and light mix for medium. Currently i use 3ml/l bio grow, 2ml/l bio heaven, 1ml/l bio bloom, 1ml/l top max

I have attached pictures of the burned leaves as well so you can see them. As far as my own research goes i would think it's either potassium deficiency or light stress due to the LED.

Looks like potassium deficiency to me.
Light burn would be focused at the top of the plant, centered under the focal point of the light.

ÒÒlegilizeitÒÒ said:

Looks like potassium deficiency to me.
Light burn would be focused at the top of the plant, centered under the focal point of the light.

Click to expand...

I just think it's weird that some plants like completely fine and others are starting to have this issue. Could that maybe mean that it's actually a ph issue since only some of the plants are having it while they are all getting the same amount of nutrients?

nac said:

I just think it's weird that some plants like completely fine and others are starting to have this issue. Could that maybe mean that it's actually a ph issue since only some of the plants are having it while they are all getting the same amount of nutrients?

Click to expand...

Nah, unless they're clones, plants can have extremely different uptake rates.
My current run had 4 plants, all GDP from the same breeder.
Not a single one of the plants grew close to the same lol
But they are all ending with that distinct purple trait

Have you tested the run off?
It looks like salt build up to me.

I’m somewhat novice with the nute issues but seeing as a lot of nutes are salts and salts have a drying (desiccating) effect, maybe the burned one needs more plain water, or some light acidification (lower pH) of its soil to help dissolve the nute-salts and then flush, if possible.
@Star Dog and @ÒÒlegilizeitÒÒ said it first, really. I’m just making an educated guess.

Some plants definitely uptake nutes differently.

I will try to flush them tomorrow and see what that does. Will update the thread once i have more info. Thanks guys!

nac said:

I will try to flush them tomorrow and see what that does. Will update the thread once i have more info. Thanks guys!

Click to expand...

Do you have anything to measure the ec/cf/tds?

Star Dog said:

Do you have anything to measure the ec?

Click to expand...

No just ph, i have never tested ec. This is my first grow with the HLG. Before this i used a viparspectra and the only problem i had with that was that the intensity of the light was too low.

nac said:

No just ph, i have never tested ec. This is my first grow with the HLG. Before this i used a viparspectra and the only problem i had with that was that the intensity of the light was too low.

Click to expand...

Ec is electrical conductivity, it's to test how much salt (Nutrient) is in the water

What is your pH going in? Potassium deficiencies are usually associated with lower pH in soil and from what I have read tend to occur with heavily filtered or RO water...I've not had this deficiency yet and I use tap and distilled water....but you are using good nutes...a little flush is a good call and watch the new growth

nac said:

My plants are having burned leaves and I'm not sure what exactly is the cause of this so i figured maybe you guys can help!

I have 9 plants and 5 of them doesn't have any burned leaves while the other 4 does. I'm using HLG 650r LED. They are all in the same tent and here are some info on the conditions:

• Temperature 21-23c lights off and around 26-28c lights on.
• PPFD around 650 - 750 and the light is around 88 cm away from the plants (34-35 inches). I am on the 9th day of flowering (after a month of veg)
• Using biobizz nutrients and light mix for medium. Currently i use 3ml/l bio grow, 2ml/l bio heaven, 1ml/l bio bloom, 1ml/l top max

I have attached pictures of the burned leaves as well so you can see them. As far as my own research goes i would think it's either potassium deficiency or light stress due to the LED.

Click to expand...

I run theese exact same lights. They are extremely powerful.... I had the exact same problems as your plants show. I couldn't figure out for the life of me what was going on. After several runs of trial and error, i found th higher away I put the light the better the plants did. LED light burn is different from HPS light burn. LED light burn shows up as nutrient deficiencies, and doesn't have the associated heat stress symptoms as a HPS light burn/bleaching.... cut off those fucked up leaves, raise the lights (dim them dow ) and I guarantee they will respond better

dopeedogg said:

I run theese exact same lights. They are extremely powerful.... I had the exact same problems as your plants show. I couldn't figure out for the life of me what was going on. After several runs of trial and error, i found th higher away I put the light the better the plants did. LED light burn is different from HPS light burn. LED light burn shows up as nutrient deficiencies, and doesn't have the associated heat stress symptoms as a HPS light burn/bleaching.... cut off those fucked up leaves, raise the lights (dim them dow ) and I guarantee they will respond better

Click to expand...

So how far away do you have your light? I'm on my 2nd run now and it's going a little better. I'm starting 3rd week of flowering today and I have also raised the light further to around 90 cm and it was around 80 ish before. I'm also trying with more nutrients since some guy told me that fixed the issues for him and he is using the same light as well.

Currently my biggest issue is that most of my plants are pale and they don't have that nice dark green color. But a few of them look good and they are the same height as the rest. Could this still be a light distance issue? I am using an app to show me PPFD and I'm currently at around 750 - 800. But since it's just an app i don't know how credible it is. The light is around 60-70% on.