This is just my opinion based off of a shit ton of research I've done while doing my 1st time DWC setup. I had roots that were starting to brown like yours, and I turned it around and now they're going insane and frosty snow white. They have fine fibers on them almost like the hair on a tarantulas leg lol. I would NOT recommend using hydrogen peroxide. Instead I would supplement a mix of two products. 1) Orca Mycorrhizae. 2) "Garden Friendly Fungicide" by Southern Ag. The first is a mix of like 14 different beneficial bacterias and fungi. The second is an incredibly concentrated (4000x stronger than Orca for this specific strain) single strain of bacillus amyloliquifaciens. What this combo will do is outcompete bad fungi/bacteria while working in tandem with your roots to uptake nutrients. This method also cured my reservoir of mold and scum. I even had mold on my hydroton rocks around the base of the plant and this stuff made it disappear. It's now immaculate at all times. If you want to go even stronger in the bacterial realm you can look up AACT teas, or "heisenburg tea". This is just my opinion and experience, but hydro majorly benefits from having a good colony of beneficial bacterias and fungis. No disrespect to anyone who goes the H2o2 method or sterile, but don't buy into believing sterile is the only way. As a side note, be VERY sure no light is getting into your reservoir. AT ALL!