Dude those lower water leaves usually die soon after sprouting anyway. In 30 years I've never seen a pair last beyond week 4. If you blow the plants with a fan the stems will thicken up a lot. Are your lights within a couple inches? If not they should be. I use CFL and rarely have more than 1" internodes, regardless of strain, it's just a characteristic of CFL grows when done correctly. It looks like your girls are stretching for light. I am using 16 23w daylight CFL's over 7 plants 24/0 and they look as good as my MH/HPS grows ever did durring veg. You probably have enough light for one plant if it's close. It is smart using that LFL, I use T-12's pointing up from the bottom with the CFL's above. This works great as long as I use LST so the spacing from cola to light is consistent across the top of every plant. If I just let my Sativa's go natural I'd have to have many more bulbs.