it seems that the general consensus here is that the soils like that have the time release fertilizers in them and are not that good for growing mj. You are better off buying an inexpensive top soil with no nutes in it and adding the perlite and vermiculite for aeration and drainage. It is usually not suggested that you should be having any nutes on seedlings until they are at least 2 weeks old. Maybe, just guessing here, the nutes that are already in the soil you are using are too much for such young plants.
I really would recommend trying to use a different soil before starting any more seeds. Like I said you can get soil, vermiculite and perlite for 10-15 dollars. The seeds I just recently germed were from a stress induced hermie and they all germed in 2-3 days then broke soil after about 2-3 days after planting them. All bagseed. If they show the taproot then they shouldnt have a problem breaking through the soil. unless something is killing them. either the soil, nutes, or over/underwatering. I could be wrong, but that is the way I see it.