I'd vote for underwatering too. No idea about the lights. I still haven't figured that Chinese math out yet. Somedays they love the lights and other days they get a little wilty when lights come on.I feel your pain brother Picasso. I said fuck it and went ahead and watered. If it was an over watering problem, I feel that IMO she would not be doing what she is doing. But this is my first time so I hope I'm right.
Most of the leaves that were yellow or more then 50 percent dead I've cut off. Are the leaves on your plants really soggy to the touch or are they crispy? Does your plant stems that the leaves are attached to feel really flimsy?
Why did she get worse as soon as the lights came on?