root rot/overwatering, can it be fixed?

Ok so my problem is basically my plant was flipped to 12/12 about 3 weeks ago, it has gradually over past ten days stopped doing anything, ie no pre flowers/growth etc nothing, lower leaves have drooped a lot and some have white mold/fungus on them along with the top of the soil.

I know I have overwatered because even after like 10-12 days the pots still the same weight and simply not dryig out at all, i suspect this is because my lights off temps are very low (14c) so soil simply cannot dry out.

So what I did was a transplanted it to a new pot with fresh soil and tried to take off all the soil from the roots, it wasnt easy and once again I fu**ed this up aswell by litterally chopping off half the roots whilst doing it.

So I did my makeshift transplant with the part of the root ball that was still intact.

My question is should I bin the plant now or is it worth holding out to see if it will maybe sort itself out given the brutal stress it has gone through?

Keep it at a good temperature during dark cycles and itll come back to life and drink the water which you drown her with.

Thats too cold for the plants at night. Do you have a fan blowing fresh air? That should help in transpiration from both the plant and soil surface.
Did you add enough perlite to the soil for oxygen and drainage? Humidity high also?

Honestly bro, mold/fungus, broken root ball 3 weeks into flower. You can still bring her to finish but your yield will be greatly affected. More of a learning exercise now. I would keep going for the education but at the same time drop some new beens. Remember sick and weak plants are perfect hosts fore pests and diseases.

Good luck bro!

^Yeah man, those temps are too low. Being that cold, and having a bunch of damaged roots, will keep the soil wet for a loooooooong time. I'd throw a cheap electric heater in there, and get a fan blowing on the pots, to help them dry out faster. The main reason they aren't doing anything, is that they have to rebuild roots first, which is being slowed by the wet soil and low temps. Sorry man, but you chose a terrible time to transplant, and, should've never tried to remove all the old soil. Damaging those roots, did way more damage than that old soil, could've ever done. Your yield will be decreased, and harvest will be delayed, but'll still be worth keeping around, unless you need to make room for others. I'd try to salvage them if I were you, and in no huge rush.