Stunted Auto Seedling

Hate to say it but if you are already having problems and its an autoflower, the chances of this truing out great are slim. If you are a beginner grower. i highly recommend not growing autoflowers to start. You will have a much more rewarding experience growing photoperiods and learn a lot more. There might not be enough aeration in the soil and the roots are rotting. looks like you are in straight coco,I would add some sort of pearlite,pumice or lava rock. also kind of hard to see the color of the leaf with the exposure of the light