I am reluctantly coming to the conclusion that you are correct on that.
Based on my tests with Mega Crop samples and how the AN PH Perfect nutes are behaving, the only thing that makes sense is that there is something biological driving these PH swings - and its in my rez and system.
The AN nutes in the rez are no longer able to hold PH. I did a rez change day before yesterday, and the PH isnt holding worth a crap. Its rising slower than with Mega Crop, but still going up faster each day.
I did several samples of Mega Crop in mason jars. The ones left open to the air turn cloudy within hours and the PH starts to go up. The ones that stay sealed stay clear and the PH sloooooooowly drifts up.
Turns out its the same for the AN nutes, just slower to react. Im assuming the buffer holds things steady as long as it can, but then its game over.
The Mega Crop had some slightly gritty/slimy build up in the rez over time, and now the AN nute also have the same build up. Its a slightly different color, but the same feel - slimy/gritty. The water in the rez is also turning cloudy and has scummy bubbles floating on it. The Mega Crop never got that bad.
This is a pitcher I use and you can see the scum line on the PH meter. Never had anything like this with Mega Crop.
The only thing I can think is that there is some sort of algae and/or bacteria just floating around in my air that gets into the rez over time and feeds like crazy on the concentrated nutes - no matter whos nutes they are.
Not at all sure how to proceed from here, but Im not freaking out just yet. I may go back to low dose chlorine and see if that helps. So far, the plant doesnt seem to give a crap about my PH problems.
If anything, the roots are doing too well and the plant is doing great other than stretching more than I thought it would.
Im going to have to trim back my new duct tape roots. They are forming a curtain and starting to cut off mist from getting to the far side of the chamber.
Im also either going to have to trim back the root umbrella or add another nozzles down below. The mist is also starting to get cut off from reaching the root mat on the floor. Its very obvious where the mat isnt getting enough mist and where it is. The areas where mist can drop down from above are super white and fuzzy, and the other areas - where the umbrella is touching the side walls of the chamber - are not growing and not as white or even a bit browner.
Im probably going to add another nozzle down low that shoots up into the bottom of the umbrella. I will run it on a separate timer just for grins and more control. I dont think I will need all that much additional flow down low.