Need Help with sprout

i have three different strains sproutin inna dome two of them popped but the shell is still on. this happened to me a couple of days ago and i gently took of the shell but then they died on me anyone got any other ideas

just leave them on untill it comes off, or wait till the plant is bigger than take off

Could be just Damping Off...

http://www.thefarm.org/charities/i4at/lib2/startsds.htm

should i leave them in the dome in the dark?