I would draw a new h2o2 bath for her, and while she's sitting in it massage the roots very gently to try and remove that built up rot. I don't think that your going to see any improvement in the roots color/health though because the plant is dead. It is going to still mature, so just watch those crystals, but your not going to see any new growth on it anywhere, height, weight, or roots. If you wanted to, you could just switch over to a clean water solution or use clearex in your res, ph balance it, and start your plants flush, after the h2o2 bath. It's not going to take up anymore nutrients, because the roots are dead.
H2o2 bath, clean water in your res (or Clearex), let em sit for 4-5 days (til trich's turn amber), then chop her down.
What color is your res container? I got me some black ones, and although they absorb light, they reflect heat, which helps keep my small res (7gal) right around 68f with me doing nothing. Not only that, but black buckets reduce your chances for algae, or bucket slime, that gross stinky shit the lives on your buckets walls. Might want to look for something darker than what ya currently got.
This is just my 2 pennies though.
At least it's not bud rot, as far as I know you don't smoke the roots....
~VLO