Probably spider mites from the looks of things, look on bottom of leaves for teensy, teensy moving dots. The brown spots ae from the young feeding on the juices in the leaves. Not sure how far in flower you may be, but probably too late except for the no pest strip in the trash can route for 12 hours, but it will not kill the eggs. Any webs yet?

But to be positive, fill out the troubleshooting form, who knows it could possibly be some of the stuff folk that guess throw out.