I’m horrible at this online… my mind says mobile nutrient deficiency. My Banana Purple Punch do this at about the same time. I usually pep them back up with a Nitrogen heavy feeding and a bit of Recharge. I grow in coco with Canna A/B and rarely have any issues other than with autos. I’ve cooked a few….🤣

Its really hard to tell with the just this picture. A few pictures and more detail is needed for proper diagnosis. We’d need to know the medium you are using, nutrients, PH, temp/humidity, feed and water schedule, what day of flower you are in, etc

She’s hungry and wants some Calcium! Or cal mag I have grown her a couple of times and she’s a good eater!