yeah.. i definitely wouldn't go in during lights out just to see how much they have grown.. that is just plain silly... don't mean to be offensive or anything, but things like that can definitely wait till lights on, lol.. trust me.. they are gonna stretch like crazy in the first week or two of flower, possibly double or triple in size in two weeks or so... not too bad ehh..
lights during the dark period can confuse plants and make them go all hermy on you.. not what you are looking for i would imagine..
..best of luck, and good luck with your grow, it truely is a fun way to spend four months or so..