Black Jack Aut

It is where the leaves have been overlapping.......leaves in shade will not go purple.........including parts of leaves.

Cool. Odd to see such a sharp contrast but I wouldn't worry so much, its clear your plant has genetic disposition towards purp.(anthocyanin). Purple colors can be accelerated by lack of nitrogen, colder temps, and excess blue light. Anthocyanin and chlorophyll have different tones purposes within the plant in general and how they attach to cells if very different. Over simplification but its something like this. Chlorypyll is for growth. Anthocyanin is more a protective measure. The normal green leaf tip must not have required as much "protection" as the parts as exposed to direct constant light.