Only 1 seedling? It all most looks like your light may be to close, I set my light so the leaves point up to the light and they are not shying away from it, you are not feeding anything yet there to small, if you are I would think they would all be like that, keep a close eye on the rest of them, there so young yet its really hard to say, a seedling is in a vulnerable state, I usually put my seedlings under a 300w light until they have grown a few sets of leaves and the main stem hardens, at this point I switch to 600w then start slowly aclimateing the young plants to food, it could be a dud bean but again keep a close eye on the others.