It looks like maybe you left the seed husk too far above your sub.. and the husk of the seed stayed attached to your girls.
They did they a little stretch.
But can be easily fixed when you uppot them and the stem has a bit of green to it. You'll be able to plant them deeper below your subs level. Making the base of your stem to your cotyledons shorter.
I think it was just a case of them been blocked by any light. Next time. Put them half an inch into the sub and when they push themselves up, the husk should be left behind in your sub.
Good Growing