Nature has it's way of doing things. Seeds just germinate at different times for different reasons. Light is a big one, as there might be a pebble blocking a bit of light, or a seed may have a little more cover. As far as I know L's are in that area between needing light to germinate and also needing a tiny bit of cover. They are in between, which actually is a quality nature has built in for tough conditions. I've grown a lot of different types of seeds over the years, and some can't really be covered at all, needing light and lots of humidity. The cacti are about as highly evolved as plants get, and these little differences insure some diversity. I lost a few of my babies recently, as I had to leave here, and have wood heat only, so they had their light but without the heat, most likely produced the right conditions for fungi spores to germinate. I didn't sterilize the soil, so this was bound to happen. The rest are seeming healthy and happy. I just raised my light a bit, as I'm learning how this new Super Nova LED light system works. The infra red part of it's spectrum is great for germination, getting the soil nice and warm, and all were quick to sprout. It was too bright, but since giving them some shade, and raising the light the first time, they are getting the right color, an some are really looking like fine little cacti. I've done this a number of ways over the years, using a greenhouse etc., this time being off grid, needing low watt usage. I've decided to move to Arizona, so I'll be like a kid in a candy store when I live in cacti land! Happy growing! Oh yes, I mixed a little slack lime in my water, which raises the pH, which fungi don't like.