Post-Germination

I am having a problem with growing lately, I have done outdoor grows but now growing indoors I am having so many problems. My main problem, My seeds will germinate with a tap root of about 1/4 inches, I plant them, I water good, the next morning out of curiosity since my last 6-7 seeds have done this, I shuffle some dirt and shure enough, the little taproot withered away over night. What is causing this. Most websites say not to over water, So I water once a day and their still dying, water alot still dies. What am I doing wrong? Thanks in advance

PS. I have read and looked at my set-up and came to the conclusion that I need to install a home-made drip system to keep the soil from drying out completely killing the plant, while also no overwatering, could this be what is killing them overnight, My medium is about 1/2 inch rocks then soil. But this medium is drying out fast,

you might try a seedling starter tray with a dome and leave out the rocks the dome should help prevent the soil from drying out to fast you dont really need a drip system just water the soil well before planting. other things could be contributing to the problem also, like how deep are you planting them as they should just barely be covered with the soil and temperature of the meduim could also be affecting it if its to cold or even to hot.