White powder on leaves

That is definitely powdery mildew. For the some homemade stuff to try get rid of it, anything from 10-50% milk mixed with water, foliar spray. But yeah, you'd typically want to be on the lower end of that. There's also stuff like citric, tartaric acid, epsom salts. Some of that you can throw with the milk stuff, just not too much, like a teaspoon per 5l. As a potential added bonus, some of that is also functionally nutrient feed (tartaric acid is potassium, epsom salts magnesium and sulphur). You'd typically want to add a little bit of plant oil to that too, maybe like half a teaspoon for 5l. Other than that, you get plant oils, sulphur, potassium bicarbonate, MKP can be useful, even just something like lemon juice, etc. I recently moved a random small plant that was almost purely white from mildew, grow entirely in shade and practically poured water+ milk + tartaric acid + epsom salts + sunflower oil sort of mix over the whole plant, and kinda massaged leaves...literally just to test if it works. It worked brilliantly, one application and all the mildew was gone and hasn't returned (though the plant isn't in total shade anymore). But of course that is not something I can recommend or would advise you do. Well, unless the plant is quite small/young/not flowering and easy to manage in that way.