PH always crashing down in DWC / Jacks 321

[Thegreywizard]

So this is my second sterile Current Culture DWC run using Jacks 321

Zkittles Auto
Single Current Culture 8g DWC bucket
RO water
Jacks 321
UC Roots
Mammoth Silica (Veg & early Flower)
PPMs - 1100 (I do a x5 on Jacks 1 gallon measurements)
PH 5.8-6.0
67* consistent temp from chiller running 24/7
AC Infinity Ionboard S24 - on 18/6 & 100% since I'm late flower and about 18" above the tops of the plant
AC Infinity 2x3 tent w/ exhaust & controller
PPFD - 650 - (Uni-T Light Meter w/ PPFD app)

So I've been using Jacks 321, following their feed chart and now at the end of flower, so I started running the Finish since Sunday.

Using Jacks 321, I generally have my PH dropping over the course of the week. Sometimes it will hold for days at 6.0-6.2

I do run Mammoth Silica in veg & early flower.

I usually try to keep PH 5.8-6.2

But I just switched to Jacks Finish on Sunday and I seem to have my PH crashing .5-1.0 lower per day, and I'm constantly having to adjust it.

Does this sound normal for their Finish?

I also use a magnetic stirrer to mix the Jacks one at a time. Usually wait about 5 minutes to let my chiller cycle before adding the next nutrient.

Any idea what is making my PH crash so much in DWC using Jacks 321?

 

[Thegreywizard]

Anyone have any ideas?

 

[josefrahl]

I get this from certain strains. Just did a Creme Mandarin that crashed through the whole cycle. Had a Green Poison going at the same time, same feed, and didn't have to rePH once. I've had a couple strains just do it in flower before as well. I think some strains just don't do well hydro, and I don't run them a second time.

As to the why? I'm pretty sure I read somewhere it's from the plant pulling a ton of a certain nute causing the PH to go out of whack.

 

[ianblaize]

What are you using to manage pH?

RO water typically has very low alkalinity making it prone to pH swings. It's fine, just needs to be managed correctly.

Also, as the plants up take nutrients, ions that were not absorbed will be left behind causing changes in pH. That's actually a good sign showing you that your plants are eating. If that didn't happen you should be concerned.

 

[ianblaize]

Read my response to this guy's post.

PH not raising with Jack and RO water

I’m using Jacks 321 nutrients schedule for the first time and with RO water. Before nutrients the waters around 7.3PH and after it dropped to about 4.1PH. I let it sit over night and it was still at that 4.1 range. I’ve slowly been adding PH up but it doesn’t seem to be doing much for the amount...

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