I've only grown it once so far(have 5 more almost ready for 12/12, right now), and if I remember correctly, mine looked similar to yours, at that stage. They turned out excellent though, and yielded well, so I wouldn't be worried about it too much. As mentioned, they are heavy-feeders, so next time around, up the dose a little bit, and see if that helps. Just watch for the tell-tale signs of overfert, and you should be just fine.