My number 1 suspect would be that bacteria product. The first experiment I would do is without that product. It's certainly not needed anyway
I started the grow without it and still had the same issue. I started using it later on thinking it would help promote a stronger root system and aid in the uptake of nutrients. Maybe stopping the crazy ppm swings but nothing...it only continued. I've always used mycorrhyzza in my soil grows and it seems to do wonders on the roots. I was hoping it would do the same here in hydro.