If you have adult protagonists, it's not YA. There aren't many adult POVs in YA either, but an adult POV who is not a protagonist is not necessarily going to keep you from being YA... but 19yo protagonists are most of the time going to push you out of the YA range. There are a few exceptions (most, not all, were not the author's debut book).
As far as I can tell, NA isn't a very popular thing anymore. I don't think it ever was outside of romance.
Who is your intended audience? Do the 19yos drive the story? Can then come down in age to 18 (I also don't know what "21 in their counting" means, but that's way out of YA range)? If you want this for a teen audience, seriously evaluate the book and whether it's written for the YA audience? Consider the adult perspectives? Are they truly needed? Do they have too big a hand in the plot? What is "YA-ish" about your plot?
If your book would appeal more to adults, market it to the adult market.
As far as I can tell, NA isn't a very popular thing anymore. I don't think it ever was outside of romance.
Who is your intended audience? Do the 19yos drive the story? Can then come down in age to 18 (I also don't know what "21 in their counting" means, but that's way out of YA range)? If you want this for a teen audience, seriously evaluate the book and whether it's written for the YA audience? Consider the adult perspectives? Are they truly needed? Do they have too big a hand in the plot? What is "YA-ish" about your plot?
If your book would appeal more to adults, market it to the adult market.