Oddly shaped leaves are usually a magnesium deficiency. However its usually good practice to really let a plant show un-admissable signs of problems before going ahead with solutions, at least in the nutrient factor. So you dont mess things up further. Go to the Growing Resources link at the top of the page and take a peek at OVERGROWS plant problem link. Its got photos and everything. Really Helpful.
Magnesium deficiency will exhibit a yellowing (which may turn brown) and interveinal chlorosis beginning in the older leaves. The older leaves will be the first to develop interveinal chlorosis. Starting at leaf margin or tip and progressing inward between the veins. Notice how the veins remain somewhat green though as can be seen in figure 15.
Notice how in Figure 16 and 17 the leaves curl upwards like they're praying? They're praying for Mg! The tips may also twist.
Mg can get locked-up by too much Ca, Cl or ammonium nitrogen. Don't overdo Mg or you'll lock up other nutrients.