Unfortunately, just a couple of hours behind a window will not be enough to finish your plants. In fact being behind glass will diminish the effectiveness of the sunlight, further complicating things for you. Cannabis needs at least 5-6 hours of direct sunlight each day to be able to function and grow properly. Any less and metabolism slows which obviously means growth and everything else slows too. Being autos they could benefit from even more direct light, so you do have a slight problem. As Mr Chevron suggested, even a couple of cheap LEDs will dramatically improve the chances of having your plants finish normally and without issues. Do you have anywhere on the roof where you could put them, even up a tree works well, most people expect plants to be at ground level and elevating them can be a simple and effective way of avoiding detection.
Hope this helps,.... Organoman.