3.5 feet away from the plants is a loooong way away for flourescent lights. The closer your light source -- without frying the plants -- the better. Flourescent lights run very cool per watt because of the length of the tube -- the heat is dispersed better than a CFL or HPS. Also, flourescent lights don't generate as much heat/watt as these other bulbs. You should be able to get them closer to 12 inches (30cm) without burning the plants. Remember, as you double the distance from the light source, the lumens drop off by the inverse square of the distance. So at 2' you get -- um -- (no good at math) -- 1/4 the lumens at the plant that you did at 1'. (correct my math please!)

The name of the game in lighting is lumens, not watts. Watts is electricity consumption (v*a=w). Lumens is light output. Different types of lights consume more or less watts for a given lumen output. The problems with flourescent lights vs HPS or MH is that they don't produce the lumens per watt that the other bulbs do, and they produce it in a different area of the light spectrum. So they are less efficient and less beneficial to yield than some other options. They are however cheap to operate, cheap to maintain, and cool to run. Since they are long and run cool, you can grow in a shorter area. So the tradeoff on efficiency might make sense if you're growing "on the cheap", in a short space that won't let you hang a hotter bulb, or in an area where heat and noticable power consumption are issues.