is your rockwool staying damp? you might want to remove the plastic that is wrapped around the cube as this can cause issues. also, how close to the plants is the 400W?

-shake
headshake Reviewed by headshake on . Leaf turning yellow.... picture! Problem: Plant leaf turning yellow Conditions: Temp: 79 Humidity: 48% Resevoir pH: 6.25 Nutrients: 1/4 strength micro and grow Vent: closet grow, door remains open, osc fan Age: approx 1 week old Light: (2) 85w cfl, approximately 3-4" from plants Rating: 5