s-d-t,
I think it was a combination of the MG being a little to "hot" (for best seed starting), keeping them a little to wet, the temperature being a little to high and the light being a little to far away.
Over all it sounds like your set up isn't that bad and should work with a few minor tweaks. Here's what I'd recomend....Get a bag of Jiffy Organic seed starting mix (around 4 bucks at Home Depot, WallMart, Ace, etc). It's finer textured and has less nutrients in it. Instead of the Jiffy "cups" use 12 oz "plastic" cups. Drill 3 or 4 1/4" holes in the bottom of them.
The Jiffy mix is a little hard to get wet initially so before you plant the seeds fill the cups, set them in a pan, water them and let them stand in the run off for an hour or so until it gets completely saturated (after that though you never let plants sit in standing water). I like to soak my seeds between wet paper towels until they just spilt open and begin to show some root before planting but if you've got good, fresh, viable seed putting it directly into the Jiffy mix is just as good. Put the lights about 2 to 3 inches over the cups, don't cover them and don't over water them. I'd try to keep the temps in the 65 to 75 range but if it gets a little out side of that don't sweat it. 18/6 on the light is good.
MG potting soil works great (if you know what you're doing). It's just a little to "hot" for good seed starting. The other thing is that to promote better drainage it needs to have more perlite added to it (20% seems to be the consensus). So while you're out getting the Jiffy mix I'd get some of that to. I'd use regular (untreated, no additional nutrient) perlite and not the treated MG perlite but if that's all you can lay your hands on, so be it.
You're going to want to get a couple of 1 gallon plastic pots also. Once your seedlings get 2 or 3 sets of leaves (around 2 weeks) you're going to want to upcan them into 1 gallon pots with the MG (with extra perlite) potting soil.
With the exception of maybe giving them a little Super Thrive after they've come up you're not going to want to give these plants any thing but plain water for at least six weeks. And don't let any one tell you you need any of these high dollar, cannabis specific nutes either because you don't.
Jack
