I am in the process of learning a hard lesson about having the soil too wet around seedlings. Before my last trip to Europe, I soaked some topsoil, and planted 20 broccoli and 20 snow pea seeds in flats. When I returned, the soil was still very wet. I had left the flats in the cold garage, and to be sure they got plenty of water I left them standing in a small amount of water. The problem is that the small amount of water really drenched the soil.
After being in the ground for about 12 days, 11 broccoli and 3 snow peas sprouted. Now, 5 days later the broccoli are all turning yellow and dieing. As far as I can guess, the soil was simply too wet. Not sure if that's what happened to the 17 pea seeds that didn't sprout. I had heard that you need to nick pea seeds because they don't take up water very well otherwise.
If I think I have time, I may try to replant seeds in the flats again, but keep them much drier. I only have until about the first of May to get the broccoli crop in, so I can't afford to lose another two weeks.