Seeds should not be watered very much at all, they have no way to deal with the extra moisture like plants due through transpiration. You are nearly undoubtably drowning your babies. When germinating, I wait until the tap root is about 1/2" long before planting 1/4" from the surface with the tap root facind down. Water sparingly every few days (I mean 5 ml or so, which is a teaspoon), and they will pop through in 4-7 days usually.