Put simply, they NEED sleep!
18 hours of lights on and 6 hours of lights off is the way to go.
For more detailed answers, please see the answers I gave arch1234 (lime green, slow growth) and djkjoe (how long does it take....) on this very same subject and on this very same page, a few questions in front and behind your question.
Apart from needing sleep to have a proper metabolism and complete photosynthesis cycle, they look just fine, with little need to worry, - they look just how cannabis plants should and the curved leaves are exactly how cannabis grows.
Hope this all helps, Organoman.