How hot is it outside? How much have u been watering? A shot glass or two is enough at that small. My guess is she got way to hot being in direct light for so long as such a young seedling. I don't put mine in direct sun till it's truly in it's veg state (first five leaves) they also love a very humid environment! Try putting a clear plastic solo cup over the girl that you sprayed water on the inside to help raise humidity you may still be able to save them! Cheers and happy growing!