You aren't *suposed* to. With organics, you need the microorganisms to breakdown the nutes into something the plant can uptake. H2O2 will kill the bad stuff (causing your root rot) but will also take out the good stuff too.
My 2 pence would be to toss in some H2O2 a day or two before a res change.
i agree with what he said. blast them with some h202. a few days later add back your organic microbial base. like some earth ambrosia or great white mychorzae.
i had the same problem use the h202 with the hygrozyme $36.95L it breaks down the rotten roots and the plant feeds off of them
i now just add hygrozyme to all my solutions its amazing
use the h202 2 tablespoons per gallon use hygrozyme as 1 tbsp per gallon
4 days change water dont use the h202 keep using hygrozyme