Powdery Mildew: 18 days flowering

Like the title says Im 18 days in flowering and starting to get powdery mildew....I figured out my room was gettting way too humid at night, so I already fixed that, now its stays at a pretty constant 50%, sometimes lower....Im hoping it wont flourish now that I fixed the humidity, but what should I do about the existing mildew? I have some of this stuff: Serenade Garden Disease Control - Safe, Effective, Organic Control of Fungal and Bacterial Diseases do you think its a good Idea to spray it with this stuff this far in? it says safe for flowers, tomatoes, fruits etc...