I found my seed's weren't sprouting, then I put a heating pad under the seed tray on low heat. It seemed like they popped up quickly after that. I think the potting soil was just a little too chilly for them. I am using a used fish tank to sprout my seeds and grow the plants in, I put empty coffee cans in there first to lift the seed tray up as close to the light as I could. (I found out later you don't need lights right away, from reading information on here). I got a lot of sprouts after I put the heating pad underneath the tray, and the ones that didn't pop up, I figured were immature seeds.
I also, just last week, started seeds using the wet paper towel method, and I checked them today, found they were just starting to crack and sprout, and just transplanted the seeds into pots. I'll see out of 10 seeds how many will make it.
I think these older seedlings, I used Miracle Grow on them too quickly, so I lost some. I am now using straight tap water and see how they do. We kill with love my friend, so be kind.