@Lindsey285 I would just be straightforward- speaking to a guest about something doesn't have to be thought of, or experienced as confrontational.
If it were me, I'd say sonething like "Hey, XX, there's something I need to talk with you about ("with", not "to" indicates a conversation, rather than a complaint).
I have assumed you're a vaper or pot smoker, due to your business, and I don't have an issue with that, because I never detected any odor on your previous stays. But this last time, for some reason, the smell was super strong, which is really unacceptable for me as a host, as the next guest might likely complain. It took me days of airing the place out and washing everything, and the odor was still strong.
I'm not sure what you did differently this time, but I can't have this happen. As you know, my listing is no smoking, so as long as you indulge outside, that's okay, and maybe keep your laundry in a plastic bag in case that's the source of the odor.
You've been a good guest other than that, so I hope we can work this out."