Stalled Seedling

in my experience of growing in soilless mediums. That plant was soaked to long before planting or the medium around the plant is to wet and it has been drowned a bit. maybe the soil is to hot "to many nutes", but i don't think so. Best thing you can do is keep temps up around 27/28 to help evaporate the extra moisture in the pot. lower back to 24-26 when its dry. keep airflow up to encourage more evaporation, but do not place the fan directly on the seeding just yet. Keep lights on medium/low as the plants in shock, back to high when it starts to show solid unmutated leaves. This plant will be stunted and behind by a week or two because of this if you decide to keep it. as a seeding, I never water till it comes out of the bottom of the pot. Soilless mediums will take up to much water for the newly sprouted seedlings, just to moist. Use humidity domes when you can, ideal is around 70-80% for seedlings. weening off to 55-60% then 45% I mix/water my soil before placing it in the pots to get the correct ratio I like also known as field capacity to me. moist but when squeezing it but no water comes out. perfect for seedlings. lots of air between the roots and medium, not packed tight - light and fluffy, high humidity keeps it from drying out. best of luck