From the deep glossy green patches on the leaf it points to overgenerous fertilizer. A leaf has a top, bottom and middle layer of cells - particularly the top layer is designed for protection, bottom layer is for gas/moisture exchange, and the middle layer, protected from above and below, is the soft biochemical factory. If the colour does not rub off, likely something has killed off the soft cells in the middle. This can happen with fertilizer - there is a carrier in the nutrient to help get it into the leaves through the roots. Too much fertilizer and the salts can accumulate with a double whammy effect: first making it hard for the root hairs to do their job and get the nutrient inside the plant, and second when the rich nutrient hits the soft leaf cells it can destroy them. The deep green sort of points to this; in some places the factory cells have survived, in other areas not.
Unnaturally twisted leaves can also point to chemical poisoning from an attempt to control bugs, maybe with a sprayer that was previously used to carry herbicides. Tiny amounts of modern sprays can have devastating effects when applied outside their normal parameters.