that's a good-draining mix, and pretty close to what i use. get one of those trays that holds rockwool cubes and drop that in a solid tray, and you're set. transplant to your pots as soon as you get a shit-ton of roots out the bottom of the cubes and you won't waste your soil on weak seedlings. with the mix i watered every other day until i got a drip irrigation system and i water less but every twelve hours ... it's pretty hard to overwater when the mix is that aerated.
Since my problem seems to be overwatering, would moving the sprout into a rockwool cube just make it worse since the cubes are going to be drenched? I'm hoping I won't have to scrap everything and start over. I just can't wait another 2-3 days for seeds to germinate lol