PH 5.7-4.7 in 12 hours. DWC

Hi all.
This was posted elsewhere for a a suspected feeding issue.. which has since began to become a ph issue too.
So a bit of copy/paste.

My set up
Single site DWC with airstone
Temps 78/70 day/night
Res Temps. 70/64 RH 40-45% Maxi bloom dry nutes RO water
NL5xHAZE
Week 5 from flip
So for the last few weeks my girl seems to be eating less and less. I was around 1000ppm at one stage early flower.. but ec kept rising as she drank water. And she's drinking plenty. Approx 25 litres every 2 days. I've res changed completely twice now. The last being a couple days ago. I dropped ppm to less then 500 and 2 days later shes drank another 25 litres but ppm has risen again! PH remains stable or slightly increases but not by much. And I keep a range of 5.6 to 6.2 usually allowing the full swing. So I'm confused.. she is definitely thirsty.. just not hungry anymore?.. or is this the start of another issue. Has anyone else had a super light feeder like this.. this stage in flower?? I did think I had a mag deficiency early on too.. but if she's not taking up nutes. Should I be surprised? Cheers JG

The problem being now... is that PH has started to plummet in record time.
As the title says 5.7 down to 4.7 in 12 hours.
No ideas as to what is causing this, ec is rising still slightly and was last set yesterday at 360ppm (0.5conv.)
400 today

Preparing to do yet another res change.. but with 0 nutes this time and just ph RO water and leave to sit for 24hrs.

Does anyone have any suggested why she's refusing to eat.. and now ph issues.

Cheers JG

PS.. will attempt to get root pics later although I don't think it's an issue and may be hard to do single handedly as she's quite large!

Here's the roots. A little staining from nutes is all I see

Thers a thread here somewhere labeled underground dwc,same problem.Reduced the N and said it was better.I looked cant find the thread.Hopefully you can.

myke said:

Thers a thread here somewhere labeled underground dwc,same problem.Reduced the N and said it was better.I looked cant find the thread.Hopefully you can.

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OK Mike nice one. Will have a look..

Remote dwc underground in grow journals i think.

hard to see correctly in the photo but them rood look very discolored so maybe the start of a pathogen

ill cop shit for saying this but no cal mag. my plants drop ph quickly if i dont add cal mag.

Octastich said:

hard to see correctly in the photo but them rood look very discolored so maybe the start of a pathogen

ill cop shit for saying this but no cal mag. my plants drop ph quickly if i dont add cal mag.

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I agree the lighting is poor to get a decent look. The top of the roots though are very pink. This is caused by the Maxi bloom dry nutes. Lights are out now. So will try again when they back on.
I must add also.. from the net pot down a few inches the roots spend a fair bit of time out of the water.
Simply because she's drinks so much so quick it's hard in a single site to keep topping up, maybe this is adding to dis colouration.. there's no slime, and the roots don't pull away and break easily.

Cheers JG

JovialGent said:

I agree the lighting is poor to get a decent look. The top of the roots though are very pink. This is caused by the Maxi bloom dry nutes. Lights are out now. So will try again when they back on.
I must add also.. from the net pot down a few inches the roots spend a fair bit of time out of the water.
Simply because she's drinks so much so quick it's hard in a single site to keep topping up, maybe this is adding to dis colouration.. there's no slime, and the roots don't pull away and break easily.

Cheers JG

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Next time add a rez,water level stays more consistent.2 bulkheads and some hose easy.

JovialGent said:

I agree the lighting is poor to get a decent look. The top of the roots though are very pink. This is caused by the Maxi bloom dry nutes. Lights are out now. So will try again when they back on.
I must add also.. from the net pot down a few inches the roots spend a fair bit of time out of the water.
Simply because she's drinks so much so quick it's hard in a single site to keep topping up, maybe this is adding to dis colouration.. there's no slime, and the roots don't pull away and break easily.

Cheers JG

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my roots often get stained. if thats all it is then i would worry
from my experiences its not a problem or the net pot to be lower. many times i dont top my res up until its half gone and many of the roots are exposed to air

hope someone can give a defined answer

Octastich said:

my roots often get stained. if thats all it is then i would worry
from my experiences its not a problem or the net pot to be lower. many times i dont top my res up until its half gone and many of the roots are exposed to air

hope someone can give a defined answer

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I was worried at first. But many have said in other posts the dry bloom nutes do this.
@myke this plant was salvaged and re vegged after I flowered when small to sex. It took forever to reveg and grew quite large.
I have 6 40 odd litre tubs ready to build a recirculating set up with waterfalls for my 5x5. But was postponed due to the time this one plant is taking. It supposed to take 75 day flower too..
Can't wait for her finish and start to new project. But expecting a decent haul of this one if I can put it right..

Follow the same thing.
Just can't understand the drop in EC the plants needing?..

How much cal/mag are you adding to your RO water?

You should take your RO water and buffer it to 200ppm with calmag and use that as a starting point adding you nutrients after and then PH to desired level.

You should find your water keeps a more stable PH that way.

1ml a litre.. takes ppm to around 250 when added to RO from the aquatics store I get it from near me.
I changed the res again today just before lights out and only used 50Litres pure RO.. nothing added... flushed straight through the net pot and hydroton

Just to add... the recent top ups I've done. Have also had nothing added to the ro.. no silica.. no cal mag.. as EC has been rising. By both our charts.. it's asking for less nutes.. although chugging water better then I do alcohol..
So full res change this time with nothing added at all.. in view of doing the same again soon but with ppms back to around 500 to start... rhino/calmag/Maxi bloom
That was the plan...

That could be part of the issue, topping up without buffering the RO first.

For the PH dropping.. quite possibly my mistake yes I agree with you.
It doesn't explain the lack of need for nutes when it was feeding at a much higher ppm.. virtually lucas/kiss.. I backed it off as again ppm rose.
Other top offs have always included calmag.
And I'm backing off using it as it seems the plants screaming at me to lessen any nutes.
It all happens so quick as she drinks lots.

coreywebster said:

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Damn, I have to save this

Therrion said:

Damn, I have to save this

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It's a good reference

Airstones can drop your pH, the CO2 creates carbonic acid.