The human eye is a poor judge of light, especially when it comes to the levels and spectrums that trees are effected by. What appears to you as low daylight levels, is probably on a massive magnitude less than the actual ammount of real daylight that appears the same to your eye. One thing you have to keep in mind is that even the best grow lights are not even close to the same spectrum spread as sunlight, a lot of the sun's light is in a spectrum that the human eye can't even see anyhow. So most outdoor lights are very narrow spectrum(being that they only need to illuminate the way for us humans) and hundreds, if not thousands of times dimmer than they appear in comparrison to daylight..
I hope that makes sense.. In other words, to simplify and summarize, I wouldn't worry about it too much
