Definitely overwatering! The plant in its first weeks hasn't developed a root system that allows it to absorb water or nutrients, so it absorbs moisture from the air through its leaves. I recommend letting the substrate dry out well and watering with less amount, making sure it dries enough. Remember that if the roots are in a waterlogged medium without oxygen, they rot. I hope my response helps you. Your plant will be fine, keep it up... Good job!