I don't mean to be rude or put you down, honestly........I'm actually impressed that your plants looks as good as they do.

I just can't at all imagine what I could add that would help you. Loc Nar gave you some good info but I don't grow with Miracle Grow and I've never known anyone in hydro to grow well with a ph of 6.8. So I have no idea what t tell you.
Except the very best of luck to you.