Moldy seeds

I put 2 seeds in a glass of water, left the water on a heating pad and covered it with towel. The seeds popped and once I saw the tap root, I planted them in peat moss pellets, put them in plastic Jiffy germination container with the dome, and put that on the heating pad. After several days they hadn't broken the surface so I checked on them, and the tap roots and the edge of the seeds where it opened, were completely moldy. What did I do wrong?