miracle grow is not a good soil to start off with what lights are you using
[SIZE=+0]have you wartered the plants have you a ph tester & moisture meter[/SIZE]
seedlings dont want a soil with nutrients in it yours has the ph will be out of wak probly about 5 when you want it between 6 & 7 when you water miracle grow nutes are released from the soil the plant needs to be at least 3 weeks old before you give them nutrients change your soil & repot