🌱 It sounds like you're already completely on top of it, and I'm not sure if it applies, but I know someone else in the forum seemed to get good results by adding 1tsp/gallon
SM-90 to their reservoir. I've never tried it myself. I use Hydroguard, which seems to control it for the most part, but I usually struggle at least a little with root rot every grow when it gets hot. We get big heat waves where I live so I know that's a big trigger. I've found that something that seems to trigger root rot for me is if I'm moving young seedling roots around. Like if I take them all the way out of the tub and put them back in, or do a reservoir change, or switch them to a different tub. It's like they really want to be left alone for the first few weeks to get established, and then they seem a lot less susceptible to root rot after that, at least for me. Or maybe it's because their leaves start to cover the reservoir, which keeps the water cooler?
In any case, I've come to realize over the last few years that it seems like there isn't just one organism that causes root rot.
There's actually tons of different pathogens, and each one causes slightly different symptoms (sometimes the brown appears only on the roots above the water, sometimes it's only below the water, sometimes it gets all the roots evenly, sometimes the roots get slimy, sometimes they get all twisted, etc). I think that's why it's impossible to find one thing that works for everyone. It's very possible a completely different organism is giving you root rot in Australia vs what's giving you root rot in California. So a big part is figuring out what works against your own unique strain of root rot, and working with your environment. 🌱