Too much of whatever you gave it. A little plant like that doesn't need much. Run some fresh phd water thru it and watch it.
seedlings need "ZERO" nutrients for the first couple weeks. you're going to burn it up by adding nutes. it's still very small, so you may want to transplant it into something with zero nutes. just be careful with the roots, and you should be fine. (don't forget perlite.)
Don't force feed the poor guy. A seed contains tons of nutrients, contained in the cotyledon leaves after sprouting. It has everything it needs for a while.