Sorry Mike,I misread your first post.I thought you were running two seperate flower rooms,one with a 400,one with a 600,my bad.
I still stand by my advice about the lights in regards to plant age.
A flip flop won't work in your setup,you need seperate flower rooms for that.What it does is switch the light fixtures on & off in 12 hour intervals all using the same ballast.One light burns for 12,the ff switches that bulb off & then turns on the other bulb for 12,the ballast runs 24 hours continuously.