Well IMO the diagnose is pH swings stress, most likely due to salt buildup.
I would treat by heavily flushing the pots with clearex and wash all the gear real good. Then I'd toss that solution and use bottled pH'd water at 5.5 with a few drops of superthrive for another day. Then I'd add 1/2 strenght nutes to the solution and plants should be already recovering by then