I'm pretty sure diseases were always problem, not just during Black Plague, and wanting to be healthy was one of the most common wishes during thousands of years history of humanity. So I don't really see any problem with "Bless you", and I'm quite doubtful of your story binding it to Plagues specifically.Thanks for the chapter!
I still think it's kinda morbid that people would say 'Bless you' as in 'God bless you' because it was back when the Black Plague was a big thing, sneezing was one of the main preliminary symptoms. So it's like: God Bless You, may He prevent you from dying of sickness.
I'm pretty sure diseases were always problem, not just during Black Plague, and wanting to be healthy was one of the most common wishes during thousands of years history of humanity. So I don't really see any problem with "Bless you", and I'm quite doubtful of your story binding it to Plagues specifically.
In my country, people say "Na zdrowie" which translates to "For/to your health" in English when someone sneezes, because sneezing is potential symptom of illness, so obviously people would wish you health when you sneeze.