Seedlings dont need nutrients for first week or so of sprouting, they produce those first round leaves (cotyledons) as a food storage if they need it, dirtweevil is correct blank soils are much better to sprout in. I sprout my seeds in a coco with RO water and they show nute burn right from sprout. Sometimes seeds just do that but I feel like you will have alot of issues with your soil. I would try to flush it alot to gt some of the ppms down or carefully transplant it into a lighter nutrient mix.