Many years ago you didn't over think it, or over love them

The pod of the seed actually has all the nutrients the plant needs for its first few weeks. All you have to do is add water. As far as your mixture is concerned, just too moist, I wouldn't worry about the lack of nutrients - In all honesty, coco is the way to go, because you know exactly what your putting in, there is no guessing, so when there is an issue, its easy to pinpoint. Remember that your plant roots need air, I firmly believe they aren't getting enough.

As for nutes, I'm not saying don't feed them, because they are a few weeks old, but I would only give 1/4 feeding per gallon, and it shouldn't take much longer (if the roots are starting to touch the edge) for the foliage up top to come in.

Keep in mind, that these guys may be a little runted for awhile, but if you lighten up on the feeding schedule, and get some more air into those roots, they'll balance out quickly