Apple stredel

I think is just the seed, nothing is wrong imo, be patient with her and she will be ok. Good luck

Hard to say she looks a little dark green but I don't see the dmg I'd expect from the high EC, but possible. Doesn't necessarily mean the ec is high just high for a seedling. High ec causes osmotic stress. Osmosis is the flow of water via transpiration. Gravity pulls water to bottom of pot. Light evaporates top couple of inches of top soil. Plant can only pull water from where roots can reach via transpiration. If there was very high rh, mixed with potential osmotic stress from high ec making water harder to pull up via cohesion-tension... Hard to say, maybe she just dried out a little too much very early,

it's strugling high EC