Is there any supporting evidence for this, its not that I don't trust your judgment, its that the sunlight wavelengths that the plant absorbs are not diffracted or refracted to cause a variation from the 12/12 scale... It would almost seem like the window is exactly the same as having it outside...... it gets the true 12 hrs of sunlight, so I wouldn't see why it is a problem. I also have a fan in the room circulating the air... So that is not a problem.
Anything else that I am doing wrong or I should fix????