the most annoying ph problem ever (please help me)

Greetings everyone, first my setup :

I have a 1.2m/1.2m/2m grow tent ( i think it`s 4/4/6 or smth) with 2x600 lights in cool tubes
I am using the aeroponic system from growTOOL (german)
plenty of ventilation ( i cool my lights separately from tent ventilation )
the room is dedicated for plants with good envoierment (25C/60% max rh)

now my problem that has persisted over 3 or 4 grows and is driving me MAD
whatever i do to my ph it drops rapidly (in less then 12 hours it goes from 5.8 to 3.8 or smth (4.0-3.5) )
when i change solution there is no problem for 1 or 2 days but after that it all goes nuts
i have tried changing nutes i went through every nute one by one (replaced booster, didn`t help, replaced aditives same shit, replaced base nutrients again NOTHING)

my res takes 180l of water and it would seem stupid for me to do a res change every 1-2 days, it takes out the point of having a hydro/aero system

i was thinking maybe not enough oxygen dissolved in water i got the biggest air pump I could get my hands on (one of those huge ones with 10 exit ports or smth) and currently have 10 airstones all over my res bottom aerating the hell out of that solution.

i set the drain hose to take water to the other end of the res so i have optimum circulation and again optimum aeration

still the same problem i have to add 3-5 ml of ph+ pro (20% KOH) to the sollution every 10 hours or so to keep the ph in a decent range.

oh and i thought maybe someone was fooling around with my grow even if it would be impossible for me to hear, so i put a second door to my room with a stronger and better lock.

the problem is still there and the system was expensive and is very well crafted yet, if i don`t manage to find the source of the problem i think i`ll burn the grow tool and piss on it and go with flood and drain or something else

p.s : i was using hesy hydro with canna boost and hammerhead
first switched hammerhead with hesy pk 13/14 than canna boost with hesy boost now hesy boost and pk 13/14 with plagron green sensation and now i`m using general hydroponics flora nutes with plagron green sensation

p.p.s i was using hesy enzimes but now i use no enzymes still no change

p.p.p.s i have cleaned the system well many times rinced-it perfectly so that`s not an issue.

please if you have any ideea that might help me just say-it, if you need some more info just ask, PLEASE HELP ME this is my most frustrating grow problem ever

Have you tried Advanced Nutrients ph perfect? sounds like it might be perfect for you(pun super intended)lol. when i used Cyco Nutrients id did not fluctuate that much. I've ran some nutes that just don't wanna hold there ph for that long. This is why i love growing Organic no ph, no ppm's, great yields once you dial in a recipe, and the best taste. Oh and did i mention NO PHing...lol

i have tried advanced nutrients long ago and was very dissapointed, worst taste ever, i was a hesi user until recently, i live in europe and i think nutes and strainis are a tiny bit different from a continent to another, and general hydroponics is an old brand
also it doesn`t change ph
my water is at 6 standard and when ai add nutes it maybe goes to 6.1 or 5.9 depending on what i use exactly, green sensation witch is an aditive is quite alkaline maybe they eat that out
changing nutes is out of the question for me because it`s not the nutes, it`s something i`m missing maybe in the envoierment maybe to high EC, if i get someone realy interested in this topic maybe i`ll post some pics with the setup and measurements

I run a small aero system, and I've had great ph results from h&g aqua flakes. I was told when I first purchased it, that it was intended to be used with aero. That easily could've been a load of crap, but I've had a good experience.

Seems to me like you are giving too much nutriment to your plant, it causes imbalances.

I used to have this problem in mid blooming (apollo 99).

Clean and cycle your System with H202, drain and rince.
Make a solution with only A+B... half the quantity recommended by the supplier.
Whatever you uses, never exceed half the manufacturing recommandation.
when you add other nutes than the a+b, once again, use less A+B
Experiment until you find your way.

I'm not a chemist but the way i see it is. Your plant consume some of the nutes from your solutions, if you give a solution too concentrated, the plant wont consume most of it. What you are left with is a very accidic solution as the plant consume water but nearly no nutrients and it only get worst everyday.

So be a little more gentle with the nutes and everything should be fine.

I like the comment advising to use aqua flakes.

I've never used these specifically but i run a beneficial tea and it keeps my ph rock steady now, for weeks at a time. I assume the aqua flakes (dried, less potent beneficials) would have a similar result.