Hi Birdie,
Been watching from the sidelines! Don't give up over a few failures, you will learn what works for your plants and environment. I'm rather into growing soil, but that is a subject and thread of its own. In my experience, most leggy cannabis seedlings are caused by inadequate light, not soil problems. The distance from your LEDs to your seedlings (and plants once mature) is critical, and requires trial and error, or a light meter. All LED panels are far from being created equal, there is so much variability in the LED panel market, and you can't know your light values at a given distance. If you do get leggy seedlings again, perhaps try to gently pile soil loosely, not packed, around the stem all the way up to the leaves. The stem will produce roots in a week or so after the soil pileup.
Keep trying, if you can grow veggies, you can grow cannabis. I promise!
Keith