I've noticed that some strains seem especially prone to the canoeing effect you describe. It seems to me to be a heat and/or light issue where the only leaves effected are always the leaves closest to the lights. As you've said, if it's just a few leaves, then I often will just let the plant be instead of moving the lights further away. Even when the leaves are canoing, the buds are still fattening up so I figure things are okay. Canoed leaves do tend to get beat up over time though, at a faster rate then other leaves. I'd still rather have a few more stressed leaves at the top, but get more light to the rest of the plant, so I keep the lights as close as possible. When I was growing White Rhino, I had quite a few issues with the leaves reacting to heat, nutrients, and/or too much light. When I grew something with Afghan genetics, I could do almost anything to it as far as nutrients and lights and it pretty much took everything in stride.