there's some obvious confusion in basic chemistry as well here. Sit down at your desk and pull out your notepad. This is important.
Never add a base to an acid. That's how you get volatile reactions. You always go basic then acidic. Not the other way.
The reason for this is say you have a solution of 4.0 at 800ppm. You decide to dump some potassium carbonate into the solution to raise the pH. Now, you see this shit floating in the solution and settling in the bottom of your res. This is called "crashing out." You've just create precipitates and completely destroyed the viability of those previously suspended minerals to be consumed by the plant. Not to mention, you've also introduced the potential for wild pH swings.
Now, let's go back to a link I posted earlier. I'll cliff note it here since there's obviously problems with following links and reading. I get it, it's hard to read these days. Can't make a tiktok or youtube video for yall, so this will have to suffice.
If you don't have potassium silicate, you should start with potassium carbonate. Add ~75ppm to your base water. This will be your buffer. You should have a pH of 9+. Let mix thoroughly. Now, add your pH up, likely phosphopric acid, and let mix thoroughly. Your target is 6.5. Proceed with adding your
calmag and let mix five minutes or so, then proceed adding each individual nutrient part and allowing to mix five minutes each. Once everything's added and mixed, bring your pH to your target. You should have a stable pH.
The reason you add the base is because it prevents the acid from running rampant and nose diving like you're seeing. without the alkalinity the acid will do what acids do, and just keep driving the pH down.
Now, if your pH continues to dive after adding an alkaline buffer, then you've got bacteria issues and should be adding some kind of sterilizing agent since there's already a bacterial culture established and trying to use
hydroguard or other beneficial bacteria simply won't take hold.