Explanation for rapid ph drop in DWC??? Can't find a solution!

Hey everybody! Lookin for a little advice...

I am in a circulating 24x5 gal bucket system with 50 gal control.
Problem starting in week 4 of flower through starting week 7 now.
I have been running DWC for some time and can never remember using so much ph upper as its requiring now. Heres a few specs:

Air temp: 67 - 75
Res temp: 65 - 72

Plenty of air through the stones, using 115L pump per 12 buckets

Using GH 3-part nutes at recommended 5-10-15
-Been trying 5 ml cal-mag or 1/4 tsp epsoms, or combination. Any suggestions?
-Using 2 - 4 ml Bloombastic
-For the first time: Adding small amounts of Canna Rhizotonic. Could this be the problem?

Ph: Stays right around 5.8 using auto-doser

PPM: Have tried from 500 - 1000 hoping to fix this problem. When I dropped the ppm, the Ph stabilized for a couple days and then resumed dropping. I highly doubt they want it higher than 1000.

I use a "Tall Boy" sediment and chlorine filter which brings the starting ppm of my water to 100-120 ppm.

I read some posts which suggested a very complete replacement of nutes washing off with fresh water to ensure getting rid of any problematic bacteria. This did not help.

The only other idea I have found searching posts for rapid ph drop is that I have root rot. They are large plants growing through a trellis system and it's very difficult to look at the roots. However I don't suspect root rot because of my industrial air pumps, plus I don't smell it like usual.

My only ideas are:

Somehow the Rhizotonic is causing the problem and should be stopped. (seems unlikely, but I don't really know)

or

I am thinking of dropping my res and doing a new batch, GH and Mag only with an application of H2o2 or bleach to try to kill anything that might be causing my issues.


Any thoughts, experiences or opinions are greatly appreciated! Has anybody else fixed plummeting ph? Especially in DWC?

Thanks for your time!

get a barreta filter it gets rid of ph up down blocks in water their about 20$ and from their it should be easier to change the ph

What are ph up/down blocks? I've been having problem moving my ph at all unless I dump a whole dropper full of ph down for a few days straight.

ph up down blocks are blocks that city puts in water to preserve ph and other things and it will ding up no matter how much ph up or down u put so just get a filter but u shouldnt have to worry about ph up untill past 8 or 9
but if they look unhealthy i would get barreta filter jug

If it were me I'd do a complete change out of nutes and throw in some hygrozyme to boot but I'm using an E&G setup. Any time I see my ph dropping I do a flush and hose out the res to try to get as many salts and whatever else is in there as possible. The only reason I use the hygrozyme is I feed my soils from the same res.

try some Epsom Salts, the amount depends on your amount of water