Dusty white or light coloured coating on leaves and other tender plant parts points to powdery mildew.
Powdery mildew is a fungus that spreads by wind, and prefers moderate temperatures and high humidity
Growing conditions such as close spacing, densely growing plants and shade can promote disease development.
Generally, powdery mildew is not harmful to a plant but can decrease vigor and aesthetics.
after taking a second look at your pic and without looking through a haze of bong smoke i would agree with Duckhead
"quote"
I've unfortunately dealt with a fair bit of Powdery Mildew and it never looked like that.
To my eye that looks like a splash, maybe nutes or a spill of foliar spray?
Is it on all of the leaves?
hope this helps