It looks like your seedling has dampened off. Damping off is the generic name given to a fungal infection that affects plants in the seedling growth stage. It gets its name because the condition causes the young plants to appear damp and soggy, limp, and wilting. After these symptoms appear, the seedling will soon collapse and die. The microbes responsible for causing damping off attack the roots of the plant. If a plant becomes infected, there’s very little you can do to save it, and the condition is usually fatal.