Can you give any more info?
did it seem hot, was the medium really dry? have you ph'd?
It's difficult to see, but is it only the leaves on the tops of the plant that are curling? The obvious thing would be to say that the leaves are curling away from the light, but then not all of them look like they are directly next to the light. And this just happened overnight? Was there anything else that you have done different recently? Sorry for all the questions, just trying to establish the cause which often helps with the solution....
Peace,
DST