Yellow Leaves Curling down - SOS !

This plant is about 2 months old grown hydro. Last week the water level was up and down because I wasn't paying attention.

The plant next to it is perfect and using the same nutes and water quality.

How do help this plant, it is currently sitting in the regular nute mix but about to die. Should it be just water without nutes because of a lock out ??

Thanks for any suggestions.

How are you monitoring your pH? Nute lockout is possible.
Is your air pump working? That plant is drooping like it's been "overwatered"
Maybe possible damage to the root system?

looks like a problem with the root system.

Are those clear buckets?? No light should get to the roots.

My primitive guess: a suspicion of over-watering as Pantera said.
Let those roots breath a bit. If and when it is on the up consider expanding the volume of medium she is sitting in.

Thank you for all the advise, will try and recover her