Develop healthy young stems by closely monitoring soil moisture.
A constantly wet substrate will encourage pathogens to attack the base of the stem, eventually toppling the plant.
This phenomenon is commonly referred to as "damping off."
Tender young stems are often at their most fragile just above the soil line, and a lack of airflow or constantly wet conditions can flatten a seedling crop overnight.
Fortunately, preventing this nightmare scenario is pretty straightforward. All it takes is some attention to detail and correctly timing each irrigation.
Let the soil dry, saturate it thoroughly, and don't water again until it dries out.