What are some causes of cannabis plants foxtailing...

Heat Genetics Age general Stress if its prone to it. Some strain fox-tail easier and that's part of its image,

Genetics, heat, too much light, not enough light, over matured, too much nutrients, and stress. I’m sure there are other things not mentioned.

Stress.

There many factors like heat, light, Rootzone or vdp if you cant exclude all those factors it can be genetics without diarie its hard to tell your other diarie with your RQS Fat Banana says, 24h light, so proably light or heat ?