The "stretch" that these lil buggers go through is (to the best of my knowledge) do to the plants looking for the 6 hours of light that they are not getting after flower, even more so if using MH bulbs to veg. Also with my grow downstairs I was able to see difference between 400w and 600w lights on same strain plants. The 400w stretches alot more than the 600w so lamp distance is key.