definitely WPM. If it is that bad at this point, throw it out.
your environment is probably at fault... hitting dewpoint or maybe foliar sprays etc.. don't want consistently wet plants.
Hello mate, i'm sorry to say that you have powdery mildew 90% sure, so i advice you to toss away this one. If you have other plant togher search some treatment to do in your environment to save the them.
Good luck!!