Week 18 of flower - PH dropping from 6 to 4 nightly

There’s a lot of information out there about dropping PH. I want to get some experienced opinions…
Currently she’s in week 18 of flowering - started from a bag seed of Astro (something). Currently feeding here very little nutrients from fox farms, EC between 350-420.
Trichomes still appear to be clear throughout the plant and my main concern has to do with the ph dropping like a brick every night. I set it at 6, and it literally drops into the 4 range nightly. Would love to know the cause and potential solutions. Thanks!

The PH swings get more wild as the roots take up more space leaving room for less water. In the future a larger res will help with this! For the current I personally have done a few different things that have worked but it depends on the scenario you are in.

When I had this issue, all signs pointed to acid rain effect which tells you to usually change the res water or lower the EC/PPM. This didn't work for me and here's why. I use RO water. RO water is a blank canvas and likes to absorb stuff. When we add PH'd water to lower the EC we are adding a substance that wants to react with things more than the nute water because it is already interacting with the nutes. When the nute concentration is lower, the PH swings can be wild. This was my issue and actually INCREASING the EC/PPM helped to stabilize my PH. Now when I add water I consider adding a small amount of nute water so the stuff the water reacts with is what I want.

RO water left to react with oxygen will become acidic slowly. It pulls available C02 out of the air causing a form of hydrogen acid to be created in the water which if course will lower the PH.

I caution you to make sure this is your issue before blowing up the EC and frying your plants. It took me time and patience to discover these details that you are combing through online as well. Hope this helps you out!

Alctrz8849 said:

The PH swings get more wild as the roots take up more space leaving room for less water. In the future a larger res will help with this! For the current I personally have done a few different things that have worked but it depends on the scenario you are in.

When I had this issue, all signs pointed to acid rain effect which tells you to usually change the res water or lower the EC/PPM. This didn't work for me and here's why. I use RO water. RO water is a blank canvas and likes to absorb stuff. When we add PH'd water to lower the EC we are adding a substance that wants to react with things more than the nute water because it is already interacting with the nutes. When the nute concentration is lower, the PH swings can be wild. This was my issue and actually INCREASING the EC/PPM helped to stabilize my PH. Now when I add water I consider adding a small amount of nute water so the stuff the water reacts with is what I want.

RO water left to react with oxygen will become acidic slowly. It pulls available C02 out of the air causing a form of hydrogen acid to be created in the water which if course will lower the PH.

I caution you to make sure this is your issue before blowing up the EC and frying your plants. It took me time and patience to discover these details that you are combing through online as well. Hope this helps you out!

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Thanks for the feedback. I’m going to give her a 2 hour flush in some clearex, then give a new 4 gallons of water and some light nutrients to maybe 600EC.

She’s been a light eater, at 1800EC she began showing nut burn (during late veg/early flower). I was hoping she’d be harvested by now but that’s not the case….

Splash Gordon said:

Thanks for the feedback. I’m going to give her a 2 hour flush in some clearex, then give a new 4 gallons of water and some light nutrients to maybe 600EC.

She’s been a light eater, at 1800EC she began showing nut burn (during late veg/early flower). I was hoping she’d be harvested by now but that’s not the case….

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You're pretty safe adding PH'd water even if it isn't the answer, the potential for harm is far less if it's not because you don't have enough stuff in your water. I did it twice before adding nutes and my plants made it through just fine. Sometimes less is more when figuring stuff out!

Splash Gordon said:

Thanks for the feedback. I’m going to give her a 2 hour flush in some clearex, then give a new 4 gallons of water and some light nutrients to maybe 600EC.

She’s been a light eater, at 1800EC she began showing nut burn (during late veg/early flower). I was hoping she’d be harvested by now but that’s not the case….

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My plants don't like going above 1400EC. Every plant is different so this may be too low for you, but my plants toggle between 1000-1400EC. My limiting factor is C02 though... I'll need a new grow room for that though. Ain't setting up C02 system in an area of the house that commonly is occupied!!

Exactly same problems here in 5gal bubbleponics bucket using RO water. My problem however is I don't chase ppm or ec, I don't own a tds/ec meter. Probably should but am on last couple weeks of flower ILGMs Jack Herer auto.
I haven't had any algae/slime issues even though minimum h2o temps have never gone below 78°F, roots are vibrant white, have alot of hairs, and tbh most of my 5gal bucket IS ROOTS..maybe 1.89 gallons of water are in my bucket at this very moment. Using Botanicaire Hydroguard to keep bacteria levels high to break down the carbs in Sweet Raw I've added during flower. I used GH MaxiGro for 3 weeks during veg and had explosive growth both roots and terminal growth even though I couldn't keep PH below 7(my ph buffers uh....for another day). I wanted to use tap but my local well water has so many contaminants(have used for soil grows and have noticed genetic mutations/hermies). I am now using GH liquid Koolbloom and dry ripening formula, along with cal mag w/fulvic acid 2-0-0. I have not noticed any explosive growth since preflower stretch, and the two days of stretch were so hot and dry RH35% in my house and high PH, I had light/heat burns pretty extensively. Plant went into shock but has come out on the other side relatively unscathed! This plant is rugged but now since flower, I cannot get my h2o to stabilize despite awesome trichome and calyx formation. Plant is healthy but has battle scars like a mofo.
Last water change was last week but even then, during veg I had a plant that the ph would drift to almost 8 and water levels were dropping almost a gallon a day! Now water levels stay relatively stable and i catch myself having to partially drain enough h2o to add PH up and replace. PH goes up to 5.8 or 6.3 and IMMEDIATELY drops back down to 4.9-5.5. I realize making a more base solution being acidic already is more difficult than the opposite but I'm shooting to allow an up drift like in veg but this hypothesis seems to be incorrect. Older fan leaves close to the bottom become necrotic and it seems like plant is pulling N from those leaves. I also do not manicure or defoliate, I don't see the need. Lights are Lenofocus 150W fullspectrum, a custom pcb board, leds and driver I've made putting out roughly another 125watts or more of the blue/red/uv and 80watts cool white t12s vertically for side lighting.

I want to do what is being brought up here and do a flush but without an ec meter, I don't want to bump up nutes in solution and compound an issue that may not even problematic at all in the first place. You know? If sh*t ain't broken, why fix type o thing.
Seriously though, I feel like this particular plant is struggling with iron deficiencies seeing as this plant has seen more alkaline solutions or is this the acid rain effect everyone is talking about?

Nickel for your thoughts.

45 minutes later...
I decided to flush and use drainage on outside crop (seeing most of US is under severe drought conditions). Replaced with "aggressive" ferts with 6.39 PH RO solution and as I drained only like what I said 1.5 gallons I now know my issue...low water levels due to displacement by root mass and plant is using as much nutrient as water.
Watching my meter every 10 mins or so, I finally see a stabilization. I'll post back again tomorrow with results but I wanted to reply quickly thanking all you scientists out there that understand the chemistry and biology of this plant. Sometimes we forget that this species of plant have evolved to its surroundings over the eons and we still understand very little overall about cannabis and life in general.

Sorry, i get all philosophical sometimes..

calicko said:

45 minutes later...
I decided to flush and use drainage on outside crop (seeing most of US is under severe drought conditions). Replaced with "aggressive" ferts with 6.39 PH RO solution and as I drained only like what I said 1.5 gallons I now know my issue...low water levels due to displacement by root mass and plant is using as much nutrient as water.
Watching my meter every 10 mins or so, I finally see a stabilization. I'll post back again tomorrow with results but I wanted to reply quickly thanking all you scientists out there that understand the chemistry and biology of this plant. Sometimes we forget that this species of plant have evolved to its surroundings over the eons and we still understand very little overall about cannabis and life in general.

Sorry, i get all philosophical sometimes..

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Looks like a magnesium deficiency to me along with the light and heat burn you already noted.

As far as acid rain effect the idea is the more oxygen you pump into your res the more water will react with C02 forming a carbonic acid that will in turn lower pH. The more "stuff" or nutrients in your water though the less the water reacts with the C02. If you are having acid rain effect, your readings will likely have your pH tanking daily while your EC/PPM are rising and the water level drops. In the past I would add pH'd RO water get the measurements where I wanted them and come back to the same situation. When I started added nutrients and raised the EC not exceeding 1.4 the pH stabilized because the water had more stuff in it. Hope that helps as that is my understanding!

Alctrz8849 said:

Looks like a magnesium deficiency to me along with the light and heat burn you already noted.

As far as acid rain effect the idea is the more oxygen you pump into your res the more water will react with C02 forming a carbonic acid that will in turn lower pH. The more "stuff" or nutrients in your water though the less the water reacts with the C02. If you are having acid rain effect, your readings will likely have your pH tanking daily while your EC/PPM are rising and the water level drops. In the past I would add pH'd RO water get the measurements where I wanted them and come back to the same situation. When I started added nutrients and raised the EC not exceeding 1.4 the pH stabilized because the water had more stuff in it. Hope that helps as that is my understanding!

Click to expand...

I guess some of us are still so proud of our own findings that we forget to consider other ideas and in this instance, you skipped over critical information relayed to you. Trust me, I understand atmospheric principles just as your acid rain hypothesis but friend, theories are not fact or at least with your inputs on it(you added facts that you understood but not all aspects that directly correlate with acid rain effects). Now, i don't claim to have answers to everything, especially with cannabis but friend, look, your idea doesn't explain Astros or anyones but your owns true issue, it's merely an opinion and I respect that fact but consider the big picture and take off the blinders.
Sorry but I don't necessarily agree as these carbonic acids along with whats called cyanuric acid(cyanuric bromide, cyanuric chloride, cyanuric flouride), can be measured via litmus and these very acidic molecules just don't register in my very isolated situation. Oh, by the way i forgot to mention I use ebb and flow principles in my dwc, variables like that along with the fact I also use misting nozzles and a water pump to splash roots at specific intervals. I get Google can really be useful to gather info but experience sh*ts on internet wisdom.
Hope this reply helps you as well.

calicko said:

I guess some of us are still so proud of our own findings that we forget to consider other ideas and in this instance, you skipped over critical information relayed to you. Trust me, I understand atmospheric principles just as your acid rain hypothesis but friend, theories are not fact or at least with your inputs on it(you added facts that you understood but not all aspects that directly correlate with acid rain effects). Now, i don't claim to have answers to everything, especially with cannabis but friend, look, your idea doesn't explain Astros or anyones but your owns true issue, it's merely an opinion and I respect that fact but consider the big picture and take off the blinders.
Sorry but I don't necessarily agree as these carbonic acids along with whats called cyanuric acid(cyanuric bromide, cyanuric chloride, cyanuric flouride), can be measured via litmus and these very acidic molecules just don't register in my very isolated situation. Oh, by the way i forgot to mention I use ebb and flow principles in my dwc, variables like that along with the fact I also use misting nozzles and a water pump to splash roots at specific intervals. I get Google can really be useful to gather info but experience sh*ts on internet wisdom.
Hope this reply helps you as well.

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So you don't agree? That's OK and that is your opinion. If you have some facts to share totally open to it. I'm always open to facts but no need to assume my pride or hypothisize why I may have decided to share something. It adds no substance and comes off as rude like you know me. I wasn't so proud of my research, just trying to share and help where I think I can. If I get something wrong I'm always open to correction but no need to surmize or get personal. Just the facts maam!! Happy growing!!

Thread death most likely
Thanks for your input Miss.

calicko said:

Seriously though, I feel like this particular plant is struggling with iron deficiencies

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looks like nute burn led to nute lockout to me.

EC meters are cheap: a worthwhile investment