wow i've never seen things go so wrong so quickly, but fixable. My first thought is root rot, this is prolly what caused what i thought was magnesium def. Root rot looks like a brown goo on the roots, and will always lock out some elements or nutrients or water or anything. Thats what i see on the bottom of your cups. It can also be a bacteria, i forget the name, from a water change. And you can't fix it with another water change. You need mycorrhizae. These little buggers will eat the other bacteria or root decay and then give you more nute absorbtion once they take over the place. The only company i know that sells this stuff cheap is Earth Juice. Ten Dolla. If you can't find it around; you might have to go hygrozyme or one of a handful of others. I've also heard h202, hydrogen peroxide, read up on that cause I haven't used that. That will kill all bacteria in your res. Since I've been using mycorrhizae... I a) haven't had a problem, but more so b) don't want to kill everything in my root area.
First thing mist them with a spray bottle until the goo comes off. Do this over the bath tub or sink or whatever but you'll need a lot of water. You're girls are gonna stress the next couple of days, but I've seen plants recover from this. They were in veg, but if what i see in the pics is what i think it is, you'll need to clean the roots. Have you been using the fogger the whole time? I would raise the water level to meet the cups, thus going straight dwc, add more airstones as already said, and cut the dripper and fogger for the next couple of days until we know we can move forward.
And thats the hard part. Root rot (look up pythium) will cause all these things. But I've never seen it get a hold of a crop so rapidly. There's most likely a lot of dead plant matter in your root balls, so don't be afraid to blast it out of there with the spray bottle. I had one once that I was pulling dead roots out of. Your root mass doesn't look too big so you need to save what you can, but if it looks dead, like leaves, I would remove them. Also 6.0 ph and keep your nutes at 1/4 strength (700ppmish.) There's a good chance they haven't gotten any nutrients in the last week or so, but we want them to be able to absorb what they want when they do get life back into them, DWC will allow this nicely. Your water temp and lights are fine. Like I said this is step one, aside from these couple of pointers, I'm baffled. I've seen this before but not one that took over this quick. Damn bro, let me know how things go... even my head hurts on this one. I'll check back later.