Big Chunk of my rootball just fell off =S *reposted into the right section*

Hello RIU

Ever since i started this grow the roots somehow found a way own into the reservoir in every pot and this hasnt been a problem until now... A big chunk of my rootball fell off while i was changing the water in my reservoir (i am using a 12l aquafarm) what am i supposed to expect now? can i somehow better the situation or should i just accept my blunder and face the fact that i might have killed my biggest girl? The chunk of roots that fell off was approximetly the size of half a tobacco pack when i squeezed all the water out, an equal amount of roots is still in the reservoir+ whatever is embedded in the coco.

It was made clear to me in the previous thread (i posted it in this same post in the wrong section earlier) that i might have root rot and that i should use h2o2 to combat this. However what conecntration of h2o2 do u recommend and should i use it every time I water?

I was thinking of giving it Atamis Rootfast but does it work this when she is already flowering?

What should i do to prevent this problem in the next grow? im seriously thinking of smashing the living shit out of thoose pots when im done with this cycle....

I clean and change the water in the reservoir every third day (on the fourth the its usually so dry that the pumps barely pump up any water)

Strain: Barneys farm LSD
Lighting: 400w+600w
Nutes: Atami Coco A+B 4ml/l, Atazyme, Ataclean
4 weeks into flowering (and looking great)

Thanks in Advance RIU​