Rick: If your seedlings dropped their cotyledons (seed leaves) AFTER they had other leaves, this is normal. The seed leaves provide a store of energy (and, I think, basic photosynthesis), and shrivel up when other leaves come along. Mine usually drop off after the second pair of true leaves. If they dropped off BEFORE you got any other leaves, you probably have some soil-borne fungus (like damping-off disease). Let us know. Robert.