The next time you add perlite, mix it into the soil. Sprinkling it on top does no good.
Miracle Grow soils are a bit hot for seedlings, but just keep in mind it already has nutes. It's good-to-go for about a month before needing to start a regular nute schedule. I used it very sucessfully for years, and the soil I use right now is even hotter.

Ease-up on watering, but don't let it remain dry for more than a day. Don't add nutes or ammendments for a week or two at least, and try to keep from overheating it. You do have a fan on it, right?