Have you always run them for 7 hours? If so then it's possible that it's a few other things like irregular water changes, overfeeding, dirty filter media and of course co2. How are the plants doing? Any signs of a fertilizer imbalance?
Clean everything you can, do two water changes a week to keep things extra clean while you're fighting it, cut whatever leaves that are covered out of the tank, scrub it off of any decorations you can, spot treat any remaining algae with glute (Excell) and try to get your co2 levels up high enough to turn your drop checker a light green if you can.
These are the steps I took to wipe it out when it hit my tank. I also added a true Siamese algae eater and he was another help. He wouldn't have been any good without also doing every other procedure I mentioned. He does seem to help keep it from getting out of hand once you have the BBA on the run.