That is very low base water indeed. Is it well water? That to me suggests it does not contain usual public water treatment of chloride (mainly), cal and mag potassium and trace elements. Good tap water is very low at 0.25.
If so, that means two things. Bacteria are certainly present (no chloride) and pH will swing madly because the water is not buffered. Air is certainly more than enough, probably helping loads as it is. Use this recipe to "diagnose", you're not in emergency mode. And adding lots of stuff the pH is going bananas...
Dump the rez and fill it up. Add 2ml/L of liquid silicon, let it mix extremely well, 2 or 3 hours. pH should skyrocket. The add Cal Mag and let mix another hour or two. If Canna mono nutes, add first cal let mix very well, then mag. Depending on the brand, pH may drop a little, but still high. Slowly add pH(-) until 5.6 - 5.8, don't be picky. You want the final EC at around 0.3/0.4.
This will pH buffer the solution and give a good base feed.
Next day, pH may rise, even to 6.1+ Oxygen from the stones raises pH. The more air, more oxygen. But it will be a stable value.
Add part A, let it mix well, 1h
part B, 1h.
4ml Cannazym, same drill, same drill, 1h ... I know its a hassle, but you've got 8x 55L = 440L to mix well
2ml Rhizotonic (again pH will rise), and let it go loads.
A few hours later check on the pH and correct it back down very slowly until 5.6 - 5.8. In theory, this should do it, and the roots will love it. You've got plenty of bubbles to add to the party. h202 did nothing for me to be honest, and since brewing my own beneficial bacterial I've never looked at chemicals. I would save the hygrozyme as a last defense in case of a serious outbreak.
And take it from there, keep posting and we'll figure the next step.