It's kinda RO water - I'm using zerowater filters which literally filters to 0-3ppm depending on filter age. I use the same RO water in humidifier, which has had me wondering - I think it's my last potential contamination point. It's a 5.5l res and if there's 0ppm and no sterilising agents in the water, that stuff's sitting in a warm tent all day. Gets through about half a tank in a day, and I'm only letting it run completely dry once a week for a clean. I have an output fan and since I'm vegging I have no CF on the end of it at the moment. The air is getting replaced in the tent around once every 6 minutes by my calculations, and it's only a small plant. It's also a small tent, meaning wherever I position the humidifier or the fan, at least half the humidity generated is always blown directly to the plant... my theory was that the positive pressure generated by the pump into the res would stop amything contaminating the water, but maybe contamination is via the stomata? I've got a hygrometer sat next to the plant so I know that setting the humidifier to low output and 45% humidity, the plant on average remains at 55% humidity.
I have a small piece of filter in the pump which is cleaned and anti-bac sprayed weekly, and I vacuum the lounge twice weekly. All of this leaves me thinking that the use of humidity is the final weak point.
I'll never use a Heisenberg tea again - it's intensified the problem so quickly it's unreal. But filtering 5 galons through a zero water filter takes forever, and I don't see the point in wasting the time or the nutes if this plant is now completely passed it.
Like I say - I've tried everything now. Sterile, bennies, heisen-tea... silicon and additives vs raw nutes only, and the outcome never changes. Feels like it's time to give up on hydro (or DWC, at least). As you say... there's something off in the environment and I just can't figure out what it is.
I went with DWC for speed, but like I say - if I'd just gone with soil in the first place I'd have had at least one good crop by now.