I have no idea what's wrong with my poor spider plant! D: Please help?

Your plant is in shock.That is why he is dropping his leaves.Don't water him for another 2 weeks ,till the soil is really dry.Use regular tap water , at room temp.,only enough to moisten the soil. Don't give him anymore vitamins. Also the room temp may be too cold or too hot or there might be a draft nearby.The leaves will grow back by next year,but you need to back off in your kindness or you will kill spidy.Or go to a garden center and start over with one of his brothers, now that you know what not to do.