33 Days in, 600W DWC, Plant Bottoms Yellowing, nice PICS & lots of Info

aleksandr2010

Active Member
Hi all! First, some background:
4 plants, all AK-48 (Indica)
This is my 2nd grow, first one with DWC. I am 33 days in, with day 1 being the day the seeds were dropped into the germination glass.
5x5 mylar tent, 600W HID always about 19" from canopy top.
4 plants in 80 L of DWC water in 3" trays, several large airstones. Water change every 8 days.
Ph: between 5.8-6.3
PPM: tap water was at 190, starting PPM with total 10 ml of nutes was 240, now PPM is around 450. PPM does not change much as water gets obsorbed; currently crawls up a bit, so its a *bit* high.
Water Temp: 70 F-80 F depending on time of day
Air Temp: 23 C - 33 C
Nuts: Advanced Nutrients SensiGrow Parts A+B only currently. I put in *slightly* more Part A since that is the N heavy part and they are still fairly young.

I noticed a couple of days ago that the bottom leaves on all of the plants, the leaves which only grew 3 fingers, started turning yellow at the tips. Now they are mostly a light yellow and on a couple of plants they have basically died. As you can see from the pics, the top of the canopy is very healthy and it remains healthy down the middle. It is only on the 3 finger branches. Any theories? I would suspect lack of light, but as you can see in pic #1, some of the ones turning yellow are actually still getting light exposure. pic #2 shows the yellowing leaves under the canopy. pic #3 shows a plants from top to bottom. and pic #4 is just for your pleasure of the whole picture.

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Bonzi Lighthouse

Well-Known Member
Calabrate your Ph Pen, calabrate your PPM meter.

Bump your veg/growth nutes up. Bring your Ph down a little 5.8 shoulfd be the top end.
 

sk8disgruntled

Well-Known Member
time to raise that ppm. i got mine up to 750 this weekend they were 3 weeks old yesterday. only one plant is showing slight burn but i think she will be fine.
 

aleksandr2010

Active Member
Calabrate your Ph Pen, calabrate your PPM meter.

Bump your veg/growth nutes up. Bring your Ph down a little 5.8 shoulfd be the top end.
PPM meter (Nutradip Trimeter) was calibrated at the beginning of the grow. 5.8 at the top end? I always thought 6.0-6.5 for soil, and 5.8-6.3 for soiless. Source is Cervantes Horticulture book.

time to raise that ppm. i got mine up to 750 this weekend they were 3 weeks old yesterday. only one plant is showing slight burn but i think she will be fine.
I really want to go easy on PPM. I'll boost if i got to, but is 450 PPM on day 33 really causing the issue here?
 

Bonzi Lighthouse

Well-Known Member
I run my DWC at 5.3-5.8 as per me and my personal experience. (and the label on the Ph down bottle).

I think your Ph is fine it's your PPM that needs adjusting.

You want the Ph to move in order to get the full range of nutes.

 

Irollfatties

Active Member
I agree the ppms need to be bumped up, but do it slowly. Your plants look fine, no need to jump the gun and increase the nutes heavily. I thought ph of 5.5 was okay to til i started seeing mag defiencies everywhere. I now keep it strictly between 5.8 and 6.0
 

sk8disgruntled

Well-Known Member
yeah i let my ph range anywhere from 5.5-6.5 before i do any adjusting. like i said my plants are 3 weeks at 750 ppm and look very healthy
 

aleksandr2010

Active Member
alright, well with 3 people saying to bump the nutes i guess i should. I bumped up the PPMs to 575 or so and dropped the pH range to 5.5-6.0...I'll let know whether it'll get better or worse.
 

aleksandr2010

Active Member
Hey guys just an update...PPMS are now at 760, pH is between 5.4-5.9...The plants deteriorated for about 24 hours since my last post, eventually with all of them showing bottom damage and even some on the next node up but now the damage seems to have stopped spreading. I am also now 95% sure that the problem is Nitrogen deficiency since it is clearly spreading from teh older leaves up and it fits the physical characteristics of N-defiency. Here's some pics showing more progression. Any further comments are appreciated.
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