Droopy Lower Leaves

My girls on in the 23th day of flowering. Plants are doing real good except I have droopy lower leaves which turn yellow and fall off.

I have ebb & flow hydro unit and I water every 3 hours for 15 minutes while the lights are on and no water during dark period. I have been watering this way since day one without any problems. The only difference is I have added a 100W CFL.

What's wrong?:confused: Please help> :o

k, i turned off the CFL and my girls look alot happier. The leaves have stopped drooping. Can anyone tell me why this should be?