What kind of light? I hope 5500k and above as say a 2700k bulb will grow tall. So is your spectrum (k or kelvin aka color of light) correct? If so I cant see what could be wrong besides not enough light. The fans are a good idea, not only to strengthen, they need the saturated area of Oxygen around the leaves to be moved.

So, what k? What kind of lights?

Is the room temp. at 70, or is the plant area at 70. The fan is a good idea as any extra heat from the lights wiil be blown away. I also agree with MasterGardner on blowing away the oxygen and strengthing th plants I do OK with 4100k and a fan for constant air movement with a room temp. of 65-68

70F is too warm for best compact growth, but it sounds like there isn't enough light besides.

Suggestions: try for a cooler area (no more than 65 degrees once seedlings have sprouted, more light intensity and shorter growing time indoors (a lot of people want such a jump on the growing season that they start seeds too early and plants get spindly before they can be planted out)).

You need the fan to strenghten . also move the lights with in 2 inches of tops of plants ,no more than 12 hours of light