I'm killing one of my babes!!!

got four sprouts going...and they all look stellar except for one (the runt)
it's leaves are slightly yellowing and beginning to droop (I'll post pics if I can find batteries)
all four plants were treated totally equally.
I can't for the life of me think of anything that could have gone wrong

(is it possible it's just not "meant" to grow???)

thanks,
Kiddie

I've had a couple like that, same conditions and one sprout just doesn't want to grow right, don't really know what it is, i just let it keep growing until it either gets better or dies.