Like the others suggest -- way overwatered. Leave it alone and see if it's strong enough to recover. Remember, in nature, young seedlings get rained on hard, and some of them still survive. So hang on and see what happens.
I run hydro, not soil, because I'm a heavy waterer myself. It's not something I ever got the feel for. It would be great if there were guidelines, like 1 Tablespoon every 36 hours, or something like that...but there don't seem to be.
But you know how much you've done, and you know now it's way too much. So if it recovers, wait until the soil is dry before watering again and then water at 1/4 the level you've been doing and see if that's okay.
Don't give up! Once you figure it out, it'll be with you for life.