Dwc roots browning spot

It’s a rot of sorts.. too much mass and not enough oxygen to that spot would be my guess. Seen this before. Not sure what to advise for fixing it. Maybe cut out the spot, it won’t hurt much.. or if your cultivar is an 8 weeker than just let it be maybe and let it finish up

Use hydroguard or something similar. I’d you think it’s root rot growing. It will stop it and kill it if you use it with every feeding/res change. Get your nose real close to the brown stuff. Smell it, if it smells like fish tank crap or real nasty it’s root rot. If it smells like earth your ok, could be brown algae growing which does happen and it’s not as serious as root rot. Again if it is hydroguard or something similar will stop and kill it if used regularly. I grow in DWC hydroponics and ran into both root rot and brown algae and recovered from both udon hydroguard