NFT pH Dropping Week 6 Flower

[DeeJay13]

High all
Wonder if anyone might be able to help me with a weird thing I am finding.
It's my first NFT grow, and all has been great up until about 2 weeks ago.
I am now at the start of week 6 flower and have been flowering with GH Flora/Micro/Bloom as directed on the bottle for hydro.
I've noticed 2 things recently...
1. The tips of the leaves have got tiny white ends to them. I am thinking possibly slight nutrient burn.
2. The ph of my reservoir has been dropping a lot.
I start with mixing a small amount of CalMag with my water, then adding Micro, then Grow, then Bloom at the correct ratios. This usually brings me to a ph of 5.8. Perfect. No ph up or down needed.
I have been feeding my plants nutrients for 2 weeks at a time, topping up as needed, and then flushing for 48h with ph'd water and Florakleen.
Then back to the next 2 weeks of nutrient solution.
When I put my fresh nutrient solution into the 50l reservoir, and once the nutrients have been sent around my NFT system for an hour, I check the res ph and find it around 5.8.
The next morning, after 12h of darkness in my grow op, I test the res and get a ph of 5.5 or so.
By the time I get home from work and test again its down to 5.2, and the next morning 5.0.
If I wait til the following evening its down to 4.8 and so on...
Why would my ph be dropping so quickly? Around 0.5 - 0.6ph a day!
I have read elsewhere that it is not a good idea to add ph up to the res directly. I have been increasing the ph of the nutrient solution that I add to the res to top it off, to try and bring the ph up again.
This works, but again, after a day or 2 its back down to 4.8 - 5.0...???
I have read that the nutrient solution should be halved around about the 6 week mark.
Is this correct, and would this solve my problem?
Or is it normal for the ph value to drop off all the time?
Any help muchly appreciated.
Ps: my plants are a Chemmy Jones from cutting, a Jack Herrar from cutting, 2 South African outdoor strains from seed, and a Super Silver Haze from seed. All are very healthy so far...

 

[Barney86]

Yaay another NFT grower . There's not many of us mate, glad to see you at it
pH is meant to drop in bloom though. You raise the pH to 6.3-6.5 in order to keep it sweet. If it drops to 5.5-5.7 then bring it back up.
It's partly to do with nute secretions and partly the strength of your nutes.
Post a full plant shot and let me know. what your ppm is and if it goes up or down and I'll be able to tell you what to do

 

[DeeJay13]

Thanx for the reply.
I'm enjoying growing NFT to be honest. I have the 2 clones from a mates soil grow, and am very interested to see the difference in smoke between the 2 styles of exactly the same plant...
How exactly is the best way to bring the ph back up? I'm guessing not to add ph up to the res?

 

[DeeJay13]

As of right now, 1 hour after top-up, ph is 5.5, ppm is 800 and res temp (have cooling on it) is at 21.2C

 

[Barney86]

I just pump out a couple litres and massively over adjust it so it averages back out mate. To be honest though the fact that it's only dropping now says to me your Res is off balance so probably better to just reset it.
The trick is to keep the ppm just dropping from day to day. That will make the pH swing in the right direction at like 0.1 per day at most so you shouldn't ever need to adjust it out with top up or Res change.
Which system you using ? I've got a few of the nutriculture gt205's n I fuckin love them.

 

[DeeJay13]

Grow Op...Jack Herrar far left, Chemmy Jones 2nd from left, Super Silver Haze 2nd from right, Rooibaard south african outdoor far right

Super Silver Haze

 

[DeeJay13]

Haha...my own custom setup hey.
Plumbing gutter downpipe with holes drilled in the top, net pots with pellets and rock wool cubes for the plants.
Black 50l container from hardware store with a lid for the res. Holes in the lid for the return pipes, an aerator pump, temperature control with 2 thermocouple devices blowing cool air over the res, 2 pond pumps pumping the nutes to the high end of the downpipes (the other downpipes is not in the shot), and then just LED lights surrounded by 3000k LED panels for bloom, LED grow lights at the bottom of the plants to light the up from beneath, a couple of fans for circulation, and intake fans and extract with charcoal filters... The whole setup controlled with temperature and humidity sensors... Setup is in my wendy house outside, which I ripped the roof off of, insulated the roof and walls, and then set a new roof on her...
Been quite a project, but so far so good...I like a challenge...

 

[DeeJay13]

When you say to top it up, do you mean to top up with ph 6.5 nutrient mix?
And are you still using a full strength nutrient mix at week 6?

 

[Barney86]

I usually top up at ph7 mate. That's what it comes out as so I don't ever have to ph out with Res change day. Drops to about 5.7ish by the time I need to top it up just now so works out perfect 6.3- 6.5 when it averages out.
Here's my current lot on 800ppm. If I remember correctly that's what your feeding too. I'd cut down to 500 and you'll see the pH stabilise . Mine is only a 20L Res too so you'll last longer than me before needing to fix anything.
I just follow the ppm and keep it always dropping. If it's rising at all it's too strong. Keep it dropping a little and the worst that can happen is a few leaves turn yellow and the pH stays stable as poss

 

[DeeJay13]

Sweet. Nice little grow in the roof space.
I am due to do a 48h flush on Saturday, so will follow your advice when I add fresh nutes on Monday afternoon.
PPM 500 and ph of 7. Got it.
What strain is that? Looks Sativa by the way it's stretching.
What week of flower are you in?

 

[Barney86]

Sweet. Nice little grow in the roof space.
I am due to do a 48h flush on Saturday, so will follow your advice when I add fresh nutes on Monday afternoon.
PPM 500 and ph of 7. Got it.
What strain is that? Looks Sativa by the way it's stretching.
What week of flower are you in?

pH 6.5 mate. When it drops you top it up with 7 and it will average out
Think I'm week 4 of 12/12, they've finally stopped growing now. It's ak420 from Seedstockers, not sure what the genetics are but it grows like crazy. Caught me well off guard during the stretch lol.

 

[DeeJay13]

Hey Barney,
I think I may have figured it out...
Newby error...
On the other NFT channel not in the photo, I have my Swazi girl, and also had 2 other Rooibaard plants.
4 weeks into flower (2 weeks ago) I realised that they were males, so I chopped them off at the base of the stem and threw them away.
However I did not remove the rest of the plant...
The plant has obviously died (the base of the stem where I chopped them was growing mildew), and the roots were dead and starting to rot.
Last night I removed the rest of both of the males, and threw them away.
I noticed in my NFT channel when I took the pots out that there was a powdery deposit under where the roots were.
I have now flushed fully all the nutes out (they had dropped again to ph4.8) and put 25l of clean water with Florakleen in it at ph6.4. PPM is 125.
I'm going to flush them for 2 days and do a half strength nute change on Sunday evening, and then see if they start eating again.
With PPM values pretty much constant for the last 3 or 4 days, I doubt they have been taking any nutrients in over that time.
Thank you for your help though. You have explained to me how to see when the plants eat and drink, which has really opened my eyes to how to look after them.
I suppose everyone has their "eureka" moment with growing. I had mine 2 days ago when realising the dead plants needed to come out and also realising how to see if they are eating or not.
I'll keep you posted...
Irie brutha