I'm not an electrical guru, though looking at my tank I'm thinking I'm getting there. ha!
The AH kits with two reflectors come with one ballast and electric cord. How would you control the bulbs independently? This may be an elementary question, but I don't know.
I do know that with some plants that if you get too much light going then they'll grow horizontal instead of vertical. Hygrophila Polysperma is that way.