Seedlings shriveled and yellowing, please help

I got some seeds in last Thursday (one week ago) and started germination in a paper towel. I put them in rockwool cubes that I presoaked (I don't have a ph meter nor ph up/down, so I added a bit of vinegar to the presoak). They popped out looking good after a couple of days.

Approximately two days ago they started showing signs of extreme wilting, so I added some water to the cubes (tap water, but it's only ~50 ppm here and safe to drink). They seemed to recover a bit, but now they are looking terrible again. The cubes are moist. They are in a DWC setup, but the tap roots are either still in the cubes or just barely sticking out and into the hydroton (can't quite see in there), so the bottom is being splashed by the bubbles of the airstone but there are no submerged roots yet. The resevior is at about 180 ppm of FloraNova Grow.

The pictures aren't too great so I'll give a quick description. The first two are from yesterday. The second two are from today. Notice that the set of real leaves have a yellowish band near the end, and they are severly cupped/curled upwards.

Any help is appriciated, thanks.

Overwatered. Don't water until the rockwool is dry.

I let the rockwool get completely dry before watering again and all that happened was that they are leaning over, even more wilted.

There's nothing you can really do at this point but wait it out. If they don't bounce back you just learned the hard way how not to water seedlings. Good luck to you.