looks like an N abundance severely stunted all the plants growth. everyone here is saying that it looks like you overfed~ tap water has enough nutrient in it to grow a teeny seedling, If using inert medium yes maybe do a 1/8dose or 1/4dose nutrient once, but let them take off a little before you start nuting, huge mistake. Also like people are saying you may want to make sure your mix is on par~ try copying someone elses mix, i know some people like a promix/coco/perlite . The roots may be getting too much or too little air in just promix.