HELP! DWC ppm rising PH Dropping

[DrLebron]

Hi everyone,

Second round of crop.
I've been running a Bruce Banner photoperiod, just entered 7th week of flowering, I'm giving 10/14 lights. No signal of stress untill last week (may 27th actually).

My ppm is getting higher and my pH is dropping like crazy - maybe 1/1,5 every night.

I tried everything (As far as I know), my ppm at the beginning was around 780/800, now is 470 (I've been lowering down since then).
Last night I gave a decent cleaning at my set up, inside and outside (I have a chiller to control my water temp), change my nutrients, calibrate my meters and even change my air stones to brand new ones.

Today, same thing happened, ppm up, pH down.

Here some pictures!

https://imgur.com/a/4G5FZ4P

I tried to give more calmag as a try to keep the pH stable.

Bruce Banner
7th week of flowering
Photoperiod
QB - 65w - Samsung LM301H + Deep RED 660nm
10/14 light schedule
DwC Chiller (water temps 20 Celsius max)
Inside temp - 23/27 Celsius
Humidity - 44%

GH nutrients (micro/gro/bloom)
Calmag
Floralicious
Serenade (bacillus)

Problem

Top leaves turning yellow
Buds - they are definitely not growing
*Roots - no smell, brown color (nutes), no rot
Ppm rising
pH dropping insane

[DrLebron]

Thanks for the help BU2B.

Change once again and the pH is dropping (again).
I might just lost my crop