I just tried to rub it off but nothing changedis it on the leaf or is it the leaf? Can you rub it off (or change it by rubbing it?); I ask because I'm treating a flowering plant for powder mildew, often described as white stuff on leaf, but your picture doesn't look like powder mildew.
Thanks!looking bigger and stronger everyday well done..new update are on my signature...
It's hard to tell which one it could be. :/View attachment 1807649
Seen this, thought it could help?