:(

You are overfeeding them. In woolrock and as a seedling don't overfed your system. A simple free chlorine water with some rooting agent (normally I use the Plagron power Roots or other organic rooting agent. First of all I recommend you to watering in next two days without any compounds...No Cal/Mag or Canna Aqua so far...simple no chlorine water, a good rooting agent (organic) and PH Down or pH Up of Biobizz (both organics to mange the PH set). If you want to save it ( and you need to be fast) if you have some kelp solution after this next two days without any compound, try to watering the woolrock with some kelp solution ( in a 2ml/L reason) to release some stress due to overfed and ASAP pass it to the pot where you going to start your hydroponics i asume...be fast on measures 'cause what i see doesn't seem nice at all.

@organoman i guess he is pouring from above bc the roots don’t touch the nutrient solution yet so no way that they are drowned. The leafs are far away from the Rockwool so i think he is not pouring it over the leavs. Seedlings do need high humidity otherwise they close their stomata and look like this. I don’t say that it has to be a humidity dome, could also use a humidifier

Seedlings do not need humidity domes! Looks like "drowned" root zone.........stop pouring from above and let the roots go down into the reservoir and get their water/nutrients that way only.

You could take Plastik water bottles cut them in half and use them as humidity domes, this would be an easy quick solution of this problem for the moment

50% humidity is not enough for a seedling. 75%-80% and they will be happy again soon.