Powdery Mildew on Euphorbiaceae
I’m having an awful time with mildew (or some similar fuzzy gray fungus) on Euphorbias in my house, one room in particular. I tried neem oil, but that just makes everything defoliate. Then I tried spraying with basic copper sulfate (it was the cheapest and least toxic thing I could find at the garden center), but that has no effect. So I’m looking for something not found in nature, ideally something that’s illegal in multiple countries. Bonus points if it’s a yellow-green liquid that produces its own dry ice fog. Can you recommend anything?
Pedilanthus tithymaloides w/fungus
Euphorbia drupifera w/fungus
 Affected so far: Euphorbia milii, Euphorbia drupifera, Pedilanthus tithymaloides, Synadenium grantii, Euphorbia bougheyi variegata, Euphorbia trigona, Euphorbia lactea, Pedilanthus ‘Jurassic Park 2.’