Hi
@ThatGuyWhoFishes! You can use a wet tissue/paper to clean as many leaves as you can, then mix organic apple-cider-vinegar with tap water, and use it as a foliar spray. Neem-oil can also help stopping & preventing powdery mildew (few drops of neem oil with water as a foliar spray) and it's also a good way to prevent from any pest invasion. If none of these "DIY" solution show quick results, I'd use LeafCoat from Biobizz, it works great for this kind of issue. Finally, make sure your air-flow is OK, judging by the number of plants in this room I'd use at least 2 fans, gently blowing onto the canopy. Hope this helps, keep us up-to-date and happy growing 👊