I mean he def could be right... I had a shitload of pollen fall on my outdoors until todays rain they looked like shit, especially with a blurry zoomed picture, it could've been some dirt... But without going back and reading, think it was his first grow? But you're right I think I see it on more than that one leaf too, more than the ones I circled, like that one in the bottom left of the picture for example lol