First, welcome to the Garden
tybud!
Second thing you need to do is read
Agent86's Bubbler Guide Day by Day as it contains great information for any hydro grower.
Don't feed those babies anything yet. And what solution tests to 0.4 EC? (An EC of 4 btw would be a pppm of 2000 & it'd kill those babies.) Are you sure that's not reading 400 ppm?