Light burn or nute issue?

[chasingwaterfalls]

Hi all,

I realize I should be able to find the answer to this question online, but I haven't been able to.. appreciate any insight!

I'm not sure if what I'm seeing is light burn or a nute issue - the tips of all the leaves have turned brown. The rest of each leaf is fine. Any thoughts?

Long story short - the pH in my DWC is low (trying to fix it), and my led light had been too low for a while (it's now 18" away from the top)

--(pH)--
So, I'm growing in DWC, and my water has been too low of a pH lately. I was using a pH meter that has been giving incorrect readings (pH meter had said 5.5 when pH drops come out to <4). I started using pH up, but I'm still working on correcting pH.
--(light)--
My led light was like 12" away from the top for a while, and it definitely bleached a few tops (the very tip turned white). For a while, I figured the brown tips on the leaves was from the light, but this browning is happening on all the leaves equally.

 

[BuD_DizZLe]

Having same kinda problems with one of my blue OG's.
IMO its not so much light burn as it is....LED lights causing the plants to drink more resulting in nute burnt tips.
The blue OG suffering the same from this is directly under my 450w LED where the other blue OG is under a 250w HPS and showing no signs.
FYI- My led is about 14-15' away.

 

[rkymtnman]

LED lights causing the plants to drink more resulting in nute burnt tips.

that means your EC/ppm is too high.

@chasingwaterfalls : it looks like you got way too much N in your feed. and keep an eye on the yellowing all the way down the leaf. that's not nute burn but a deficiency probably caused by your pH out of whack.

 

[BuD_DizZLe]

that means your EC/ppm is too high.

@chasingwaterfalls : it looks like you got way too much N in your feed. and keep an eye on the yellowing all the way down the leaf. that's not nute burn but a deficiency probably caused by your pH out of whack.

same ec/ppm as the one under HPS and no sign of it.
Do think my ppm might be abit high tho, tap water at 150-200ish w/800-900ppm of nutes. Gave second feed about a week ago and has hardly dropped in PPM since.

 

[chasingwaterfalls]

that means your EC/ppm is too high.

@chasingwaterfalls : it looks like you got way too much N in your feed. and keep an eye on the yellowing all the way down the leaf. that's not nute burn but a deficiency probably caused by your pH out of whack.

Thanks for the heads up. I was planning on just topping up my res until harvest, but I might just go ahead and change it out this weekend.

Any chance you could tell what kind of deficiency it is? It's not important to know to fix my pH issue, ofc, but I'm just curious

Now that you bring it up, I do recall having yellowing leaves by this point (in my past soil grows). I'll consider the N in my nute mix, too

 

[OldMedUser]

No deficiency but an overabundance of N for sure. Most plants get those brown tips and it's no big deal. If the leaf margins start to go brown then you're on your way to serious nute burn/toxic salts buildup.

At this stage of flowering you should be using very little N. I'm not sure what nutes you are using but if it's a 3 - part feed then cut out the Grow and use Micro at half the amount that you use Bloom. Lucas formula kind of system.

They're looking pretty good so I don't think you have a lot to fret about.

 

[rkymtnman]

same ec/ppm as the one under HPS and no sign of it.

less light of the LED needs less nutes than the brighter HPS would be my first guess.

 

[rkymtnman]

Thanks for the heads up. I was planning on just topping up my res until harvest, but I might just go ahead and change it out this weekend.

Any chance you could tell what kind of deficiency it is? It's not important to know to fix my pH issue, ofc, but I'm just curious

Now that you bring it up, I do recall having yellowing leaves by this point (in my past soil grows). I'll consider the N in my nute mix, too

how much longer you got til harvest?

the area that i was looking at is at about 9oclock on your pic. there are 4 fan leaves that are starting to get abit yellow all the way down the leaf.

they will usually feed less for about the last 2 to 3 weeks of flower so i think if you just drop your ppm/EC down a bit you should make it thru to harvest no problem.

 

[rkymtnman]

Do think my ppm might be abit high tho, tap water at 150-200ish w/800-900ppm of nutes

i've never been above 1.2EC (600 pmms) just to let you know. maybe drop 200 ppm and see how they react?

 

[chasingwaterfalls]

No deficiency but an overabundance of N for sure. Most plants get those brown tips and it's no big deal. If the leaf margins start to go brown then you're on your way to serious nute burn/toxic salts buildup.

At this stage of flowering you should be using very little N. I'm not sure what nutes you are using but if it's a 3 - part feed then cut out the Grow and use Micro at half the amount that you use Bloom. Lucas formula kind of system.

They're looking pretty good so I don't think you have a lot to fret about.

I'm using lucas ratio for micro+bloom (6/12) plus floralicious+ and koolbloom. I'll look into where I can cut down on N a little.

I have heard from others that led lights "burn" in a slightly different way, but I've also never seen the brown tips get this bad.

I'm about 30 days into flowering (35 from 12-12 flip) and thinking it'll be another 30 days

 

[chasingwaterfalls]

how much longer you got til harvest?

the area that i was looking at is at about 9oclock on your pic. there are 4 fan leaves that are starting to get abit yellow all the way down the leaf.

they will usually feed less for about the last 2 to 3 weeks of flower so i think if you just drop your ppm/EC down a bit you should make it thru to harvest no problem.

I didn't know that plants feed a little less towards the end (still a noob); is it at a particular time, like when veg growth completely stops, or is it also strain dependent?

 

[rkymtnman]

I'm using lucas ratio for micro+bloom (6/12) plus floralicious+ and koolbloom.

i used Lucas for years. (just switched over to Dyna Gro) but if it were me, skip the F+ (more N) and the KB (way too much P and K). stay at 6/12, that should be perfect for the rest of the grow.

like when veg growth completely

pretty much when it puts most effort into the flowers at maybe 2 weeks to go or thereabouts.

give this a read and see why you don't' really need additives to Lucas
http://www.angelfire.com/cantina/fourtwenty/articles/profiles.htm

 

[chasingwaterfalls]

While I have you guys, I could use your help again =/

I changed the res out completely, using 6-12 lucas with only hydroguard, and am currently using pH drops and a calibrated meter - water's set at 5.8-9.

The leaves have begun to yellow and form brown spots. Is there anything I can do to help the plant out besides making sure I fixed the ph issue?

I'm getting nervous, plant isn't smelling as dank as it used to either..

 

[OldMedUser]

Your getting toxic salts buildup in your leaves. They'll go all hard and crusty and it'll keep getting worse. You should cut way back on the feed at 5 weeks. 500 ppm with as low N as you can manage. Some epsom salts for the S to boost resin production.

I've done 40+ DWC grows and had that happen often. You can't flush it away and the buds will steal N from the fans if they need it. When everything is just right the oldest fans will start going yellow and limp around now and almost all the leaves but the sugar leaves in the buds will be getting yellow at the end. I used to think it was great the way all the leaves would be still dark green at the end of flowering but that just meant there was too much N available to the plant when it really didn't need or want much. As N is a mobile nutrient the plant will take what it needs from them.

Check out some of the plants organic growers end up with. Usually lots of yellow and other fall colours when they are near to done.

 

[rkymtnman]

Your getting toxic salts buildup in your leaves. They'll go all hard and crusty and it'll keep getting worse. You should cut way back on the feed at 5 weeks. 500 ppm with as low N as you can manage. Some epsom salts for the S to boost resin production.

yep.

@chasingwaterfalls what is your ppm with the 6/12?

 

[chasingwaterfalls]

yep.

@chasingwaterfalls what is your ppm with the 6/12?

Ppm meter read 600 this morning (I unfortunately don't know anything about what conversion it's using).

If I've taken care of the ph problem and lessened nutes, is there anything I might be able to do to help - or do I now just have to wait and see?

 

[eyderbuddy]

I'd recommend an urgent dose of Foliar Silica, followed by Foliar Cal-Mag at the lowest effective dose you can come up with it.

 

[chasingwaterfalls]

I'd recommend an urgent dose of Foliar Silica, followed by Foliar Cal-Mag at the lowest effective dose you can come up with it.

I've never even looked into foliar feeding, but I will now..

Just doesn't feel right waiting and doing nothing when my plant's not doing too well

 

[OldMedUser]

Don't be foliar feeding anything unless you want to be smoking it with your buds. You don't need any more mineral salts in those leaves.

There should be a test members have to take before they are allowed to hand out advice. Some of it makes no sense and can be downright harmful.

Just doesn't feel right waiting and doing nothing when my plant's not doing too well

That's when most screwups happen is when newer growers just can't stand to do nothing and then do unneeded things that only make matters worse. There is nothing you can do at this point to repair the damage done, (and it's not bad at all), so all you can do is limit the progression of more damage. With the lower nute levels and pH correction you've done about all that can be done. Just keep notes about how you fed these ones and aim for a better grow the next round. I had the same problem with my last crop in pots of ProMix and kept track of everything I fed them. I'll be cutting back about 25% for this next round of this strain and see how they like it. It can take a few grows of the same strain to dial things in for a perfect run if perfection is even possible.

 

[eyderbuddy]

Don't be foliar feeding anything unless you want to be smoking it with your buds. You don't need any more mineral salts in those leaves.

There should be a test members have to take before they are allowed to hand out advice. Some of it makes no sense and can be downright harmful.



That's when most screwups happen is when newer growers just can't stand to do nothing and then do unneeded things that only make matters worse. There is nothing you can do at this point to repair the damage done, (and it's not bad at all), so all you can do is limit the progression of more damage. With the lower nute levels and pH correction you've done about all that can be done. Just keep notes about how you fed these ones and aim for a better grow the next round. I had the same problem with my last crop in pots of ProMix and kept track of everything I fed them. I'll be cutting back about 25% for this next round of this strain and see how they like it. It can take a few grows of the same strain to dial things in for a perfect run if perfection is even possible.

https://www.ncbi.nlm.nih.gov/pubmed/6100300

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0068214

https://www.pgia.ac.lk/files/Annual_congress/journel/v26/Journal-No 1/Papers/7. H.A.R.K. Jayawardana-edited.pdf

30 seconds in google my testy friend, i'm just sharing information