well let me let you in on some knowledge. I personally put my plants into flowering at 18 days old, and they were 8 inches tall. you should expect them to grow about 3x that size. the lighting you give your plant should be based on what strain you are growing. Something like auto flowering you can start at 12/12 and it will do its thing. I have some bag seed Indica that I started on 18/6 and progressed every 7 days down 16/8, 14/10, 12/12 in my opinion this is the best option because it prevents stressing.