Yes, recovery is possible.
I haven't dealt with rootrot in hydro [yet] but a treatment with peroxide, followed by a treatment with cannazyme, should serve to a) halt the rot and then b) help clean up the dead root mass.
I don't know the application rates for these treatments. Someone who actually knows hydro will certainly be able to help you, which is why I am going to stick your thread in the hydro section.
Good luck!