Your soil SHOULD have nothing in it for sprouting seeds. The only things that should be in it are whatever is in plain old good potting soil.

And by the way, how you are sprouting your seeds is the way I do it. I think it's by far the easiest way to see 100% success. It happens to also be the easiest way in general. Just keep them warm and moist. Just flood once in the beggining with water PHed to 6.8, then you probably won't have to worry about moisture for a week or two.