R.I.P. poor seedling. Have only stem right now.
Sometimes the inner endosperm layer is not shed with the seed coat and envelopes the cotyledons keeping them from opening. Gentle nudging with a toothpick or such can help to remove it. Also getting it moist by misting can help the process.
If it’s not removed it’s almost like the seedling strangles itself. I’ve even gone as far as delicately snipping the very ends of the cotyledons off to help get a better shot at removing the membrane. Have to be careful to not snap the seedling or the cotyledons off though.
1st pic, media looks over watered
EDIT: and whats with all those roots lying all around?