It is quite common for cannabis to have the odd weird leaf and not really an issue or anything to worry about.
It is not caused by anything in particular and if it is only the odd leaf doing so, it does not need curing.
Just remember, no plant will ever have 100% perfect leaves, 100% of the time.
It often occurs where two leaves have been sitting on top of each other and some slight "bleaching" has resulted.
Hope this helps, Organoman.