Ah, well then no worries-it's definitely not root rot. As mentioned, the pump looks like it's giving those roots plenty of oxygen and the H2O2 obviously helps to oxygenate the water as well. When I used h2o2 I calculated out for my buckets... 11ml/gal 2-3x per week or 5.5ml/gal daily.
Also I just realized, you said you're using Gro and Bloom? Not trying to question you're methods but the Lucas formula is Micro and Bloom so i'm curious, have you had success with gro/bloom in soil? or whatever medium you've used previously?