Is this powdery mildew? How can we know for sure?

the close up in pic 4 is not. it would look like a web of threads covering things. This doesn't look quite like WPM. Can't be 100% certain. It'll grow quite fast, so if it's not spreading it's not wpm. Usually starts in a round-ish shape and a bit fuzzy looking. Magnified it;s a bunch of thread-like stuff. here's a good example from reddit -- just imagine a smaller roundish start.. but that's how it always looked when i had it. Ther emay be other variations? if so i haven't seen them, yet. This is usually plant-specific pathogen, so should be fairly consistent.