Seeds Sprout, But Grow No True Leaves.

I ordered 6 different seeds a while back,4 sprouts out of the bunch will not grow true leaves.The seeds are all from different strains.I have let them go for weeks with no signs of leaves.Is this a genetic problem or am i doing something wrong.OPH

No one else has had this problem?I cannot recall ever having this problem with sprouts,till this bunch.OPH