I can't see the photo clear enough to see if that's actually a twist or curl.
I know that it might sound stupid but I actually get twists in my leaves all the time; some of them actually even rip. I do not know if this is normal or not, but it does not affect my plants.
I keep my fourfoot T fives about 6 to 9 inches above them depending on how big the tallest plant is. The tallest plant might be 1 to 2 inches away from the bulbs but only the red ones burn them.
I don't know what it is on yours or if it's the same as mine, but like these guys said it doesn't look that serious.
Good luck.