When I dealt with root rot nothing helped except for CX Wilt Guard. I have no idea how it's not more popular to be honest. When I had pyth in a single site dwc tote, I tried the peroxide method to no avail. When I tried dwc again with a single site bucket grow I got pyth again and tried Hydroguard but once again with no luck. Finally when I was running an rdwc setup and got pyth just as I went into flower I bought Wilt Guard from a local hydro shop and I could not believe how well it worked. It saved my crop and I barely lost any roots. I had also replaced every line, pump, and airstone in the system. If it were me and with a plant that size I'd root a clone from the main shoot and start over.