over or under watered ...i would scrap it n start again even if it does recover, its growth will prolly stunt for a while.if you start another now {n don't mess up!} it would b twice the plant in a month .whenever i have a prob with seedlings or clones i typically throw em out n start fresh. no point investing time energy n money into something that's fucked to start with. Also your soil looks a lil barky which imo is not good for seedlings as it promotes a good habitat for all kinds of fungus to breed.