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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.

Keep you water temps cool 18 – 25c, if to warm its gonna grow some nasties that will effect the roots. Can add in some stuff to help clear it up. Look at the directions for how to use for your nutrients. https://www.canna.ca/canna-aqua-vega User Instructions Shake Aqua Vega A and Aqua Vega B well before use Dosage: 20 ml / 10 Liter - 8 ml / US gallon (1:500) Stir well and let mixture stand for some hours Recommended pH: 5.2 - 6.2 Recommended EC for Aqua Vega A + B is 0.8 - 1.2 mS/cm (Part A plus Part B and assuming source water at 0.0 EC) Other directions Never mix the A-concentrate directly with the B-concentrate, as insoluble combinations will occur Keep out of reach of children Store in a dark place Keep away from extremes of hot and cold Over fertilization has a negative effect on the nutrient mix and plant quality Not to be used in protected nature reserves, reed beds or swampy areas, in hedges or small woods, in bodies of surface waters or near groundwater collecting areas If the solution comes in contact with the skin or eyes, rinse with water https://www.canna.ca/growguide OR https://www.canna.ca/sites/canada/files/2021-09/downloads_grow-schedule_aqua.pdf You can also look at their guides or make one. CANNA is a good brand and makes quality products. follow their directions. They don't list any CaMg in their feeding guide may not need it. check your labels and if it has Ca and Mg in it. then likely not needed. Good Luck!