I agree, do you think it's likely that the PM jumped from the squash to the cannabis? It is planted in the food forest about 150ft away from the cannabis garden. I think the problem is more so with the specific plant. The others in the garden have no issues but this plant was covered. It might be the way it grows more bushy and with lots of overlapping fan leaves while the others are more spread out. Maybe this plant is also just susceptible to powdery mildew, something in the genetics?