My guess is you need more lumens getting to the lower parts of your plants. 1 40w tube fixture likely isn't sufficient. Four forty watters aren't really 160 watts worth of power. It's 4 40 watters, and will only extend usable light just so far. (4-6 inches, max) The light doesn't penetrate far enough to do anything for the rest of the flowering plant. Flowering of any plant takes a lot of energy, and now is the time for more lighting. She scavenges from lower extremities if not fed properly via photosynthesis. (using what has been stored in the leaves)

Have any CFL spiral bulbs available for supplimental side-lighting? If not, WalMart has 'em. These will extend usable light about 6-8 inches. But then, you'll need fixtures too.

When I first started, I was using two of the 4 bulb t-8 fixtures. Mounted one on the wall, behind the plants, one overhead. Did ok for a while, but the slow going was painful. HID's help with easing that pain. :thumbsup: