Possible light burn or PH?

[hOOPSNAKE]

Hi all,

I've started some new seedlings. They're about 23 days old. They seem to be growing very slowly and 1 has started to show signs of possible light stress or PH issues. The PH was at 5.6 and 0.5ec for a week and I then brought it up to 6.0. I left it at 6 for another week (it didn't move) so I decided to bump up the EC to 0.6 and lower the PH to 5.7. After I brought it down and upped the EC, I started to notice these brown marks on the lower leaves. I googled and the pics I could find pointed to a drastic PH shift. This is my 4th grow and I haven't seen this before regarding the PH. I was wondering if I've been impatient and just overfed or is it something else. 3 other plants in the system and none of the others have any browning but one has (maybe) the claw but isn't dark green at all. All roots are white and healthy.

Any help would be great

RDWC
4 20lt bucket +1control
Fluming in control
Room is 25c during the day and 19-20c at night.
QB 132x4 3500K (1 over each plant) @ 200w total
Light height is uMol 400
Nutes temp is ambient. Beneficial bacteria (great white)
1 fan and filter (on every 2h for exchange)
1 Oscillating fan on 24h (not blowing on plants)

 

[weedobix]

its probably the led's. i see that a lot with some of my young plants (not all strains suffer from it) under led's. normally with ph you'll have a lot of twisted leaves first.

 

[hOOPSNAKE]

Thanks for the reply.

I backed the light down to 300 umol this morning to see what happens. I guess I’ll have an idea tomorrow morning if it’s any worse. Fingers crossed. Perhaps it an indica thing. I usually grow more Sativa dominant seeds.

 

[aridbud]

Thanks for the reply.

I backed the light down to 300 umol this morning to see what happens. I guess I’ll have an idea tomorrow morning if it’s any worse. Fingers crossed. Perhaps it an indica thing. I usually grow more Sativa dominant seeds.

What strain is that?

Hopefully, they'll shift gears into 4th, then overdrive. Good luck!

 

[TanzanianMagic]

Hi all,

I've started some new seedlings. They're about 23 days old. They seem to be growing very slowly and 1 has started to show signs of possible light stress or PH issues. The PH was at 5.6 and 0.5ec for a week and I then brought it up to 6.0. I left it at 6 for another week (it didn't move) so I decided to bump up the EC to 0.6 and lower the PH to 5.7. After I brought it down and upped the EC, I started to notice these brown marks on the lower leaves. I googled and the pics I could find pointed to a drastic PH shift. This is my 4th grow and I haven't seen this before regarding the PH. I was wondering if I've been impatient and just overfed or is it something else. 3 other plants in the system and none of the others have any browning but one has (maybe) the claw but isn't dark green at all. All roots are white and healthy.

Any help would be great

RDWC
4 20lt bucket +1control
Fluming in control
Room is 25c during the day and 19-20c at night.
QB 132x4 3500K (1 over each plant) @ 200w total
Light height is uMol 400
Nutes temp is ambient. Beneficial bacteria (great white)
1 fan and filter (on every 2h for exchange)
1 Oscillating fan on 24h (not blowing on plants)

It looks like phosphorus deficiency/lockout.

Usually P is locked out at a lower pH.

By the way the picture should say that leaves curl up (not down), which is characteristic of phosphorus deficiency.
https://www.growweedeasy.com/wp-content/uploads/2010/10/phosphorus-deficiency-vegetative-sm.jpg
https://www.growweedeasy.com/cannabis-plant-problems/phosphorus-deficiency

 

[Douglas.Curtis]

Welcome to ICMag!!

Check out the link in my signature on tending reservoirs, you'll find some helpful reading. They look hungry, and with an ec of only .5 that's normal. Bump up the nutes a bit until you get a slightly darker shade of green. You'll likely see growth rates and health pick up.

 

[I'mback]

 

[hOOPSNAKE]

Thanks for the replies, guys.

What strain is that?

Hopefully, they'll shift gears into 4th, then overdrive. Good luck!

Two strains. The pic is of Bad Azz Kush and the other is Triple Cheese. Both from Barney's Farm

It looks like phosphorus deficiency/lockout.

Usually P is locked out at a lower pH.

I would agree with you but the PH has been in range.

Welcome to ICMag!!

Check out the link in my signature on tending reservoirs, you'll find some helpful reading.

They look hungry, and with an ec of only .5 that's normal. Bump up the nutes a bit until you get a slightly darker shade of green. You'll likely see growth rates and health pick up.

Thanks DC. Some good reading. Seeing as they're Indicas, I bumped the ec up to 0.7 and we'll see if that makes a difference.

View Image

Did you forget to post something?

 

[I'mback]

Nope! A picture is worth 1K words

 

[hOOPSNAKE]

Nope! A picture is worth 1K words

Uh huh... A gallery of pics without descriptions ain't exactly helpful. Thanks anyway?

 

[TanzanianMagic]

I would agree with you but the PH has been in range.

"The PH was at 5.6 and 0.5ec for a week and I then brought it up to 6.0. I left it at 6 for another week (it didn't move) so I decided to bump up the EC to 0.6 and lower the PH to 5.7. After I brought it down and upped the EC, I started to notice these brown marks on the lower leaves."

If the problems started after you lowered the pH, I would say that is the place to start looking.

Hydro has a lower desireable pH range than coco or soil. However maybe the plants or these strains like the higher pH of 6.0 at this stage, where they're taking up a lot of P (root expansion during flowering) and K (stem and branches are supporting heavier foliage).

 

[Douglas.Curtis]

T
I would agree with you but the PH has been in range.

So pH is a very messed up subject in the cannabis community. The main issue comes from people treating all hydro as 'one thing,' when there are actually two main types of 'hydro.' Each type of hydro has a completely different pH range for healthy plants.

DWC is a 'roots-in' type plant. (I've typed this so many times it's ridiculous. Time to make a thread... Oh wait, I already did. *sigh*)

Read the link in my thread on tending your reservoir a few more times. If you don't understand it please ask questions in that thread because it will help everyone in the long run.

Without enough nutrients your plants will show deficiencies. When the pH stays at a specific point for a long time, the plant really needs a stronger solution to be able to absorb what it needs. Only a few elements will absorb easily at the one pH point, so a weaker solution will show deficiencies.

Either feed heavily enough a small pH change is enough, or set up a healthy pH swing and use a lower strength nutrient. The swing has to happen within 7-10 days in veg or the beginning of flower. Read the thread for more details.

 

[hOOPSNAKE]

its probably the led's. i see that a lot with some of my young plants (not all strains suffer from it) under led's. normally with ph you'll have a lot of twisted leaves first.

Thanks man. Spot on. After I turned the light down the problem stopped. It was just too bright from the start. Top work

 

[Douglas.Curtis]

The brown marks on the lower leaves is generally referred to as "pH spotting." It happens in both hydro and soil. I recently let an auto in soil dry out too much and the same brown spots appeared. Everything was perfect until the pH went out of range.

Turning down your LEDs helped because you lowered them below the struggling point for your plants. Fixing your pH issues, as previously mentioned, will allow you to turn them back up without issues.