Did you OD them on Magnesium Sulfate? (epsom salt)

Whether sprayed or watered-in...what products have you tried using to green 'em back up?

I'd go get a freshwater aquarium ph test kit as soon as posible, as you need to monitor your ph. Doesn't work for checking runoff water (the tinting of runoff skews results) but ingoing ph is very important.
After you test the water, I'd get the proper goop (pool chemicals are unacceptable) to adjust that water to within acceptable range. (6.3 to 6.9 for peat-based soils)
Then, after all that...I'd flush the crap out of 'em with properly ph'd water, raise the HID lights a tad, (less stress) and hope they recover.