Yup, looks like powdery mildew to me as well, best nip that shit in the bud while you're still early in flower, and stay on top of it throughout the rest of her life. Try to drop your humidity if possible, and there are all kinds of sprays you shit you can use for PM...One guy on here swears by this shit called Eagle20, which is used by golf courses and shit to control plant fungus' systemically. Whatever you do, don't just ignore it and hope it goes away by itself, cause it probably won't.