This is the advice I got from advanced nutes. Ignore the part about revive, it was just me panicking.
Since their reply came a few days late this is what I have done -
Cut off roots. Got a smaller bucket, phed water ( I used biobizz ph up/down which should be an organic product so the peroxide I added probably killed it
) and mixed 2ml of peroxide(6%, only I could find) per liter of water. I let the plant and the roots sit in it for 2 hrs. Plant looked very sad after an hour, however once I came back after the 2nd hour elapsed she was perked up already. After that I changed it into base nutes, voodo juice, rhino skin and hydroguard. If I recall off the top of my head, it took her between 4 and 7 days for the first new roots to be seen. I changed all pipes and airstones. Bucket cleaned with isopropyl alcohol.
P.S. I haven’t dunked anything in the rockwool etc as AN recommend. Literally only the steps above.