Water and a few drops of chlorine, nothing more is needed. Don't try to "reinvent the wheel" if you don't have to. You only need a clean and sterile rooting chamber. That's the main problem here. I never spray my clones. I fill the "bucket" and forget about them, two weeks later they all have roots down to the bottom.
Cyanobacteria can be devastating in hydroponics, aka "brown slime". Get a chlorine meter or strips and run 0.5ppm residual in the reservoir. You could even go higher than that if the problems persist. If you don't want to buy a meter or strips you could also use a chlorine dilution calculator, this should either way be your first measure.
Here's a link:
https://www.publichealthontario.ca/en/health-topics/environmental-occupational-health/water-quality/chlorine-dilution-calculator