What do you mean the leaves are curling up? do you mean twist, curving down like a claw, or something else.

You'll also need to tell us about the conditions. What size and age is the plant, what type of soil and size of the pot, what type of nutes, and what kind of lighting.

Pics would usually answer most of those questions too!:thumbsup: However we need to know which kind of twisting your having, and all the other stuff to give you ANY accurate info.