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.