the first looks like cold damage to me ... which is weird this time of year ...

the second is bug/slug damage.. something is nibbling on the surface.. and then those harmed cells dry out and brown ... do check for bugs/slugs after midnight.. if you havent already ...

if you are suggesting that RFS has regressed in 2 years.. being better previously.. then it is time to dig it up.. find out if there is root competition ... and throw it around the yard.. and threaten it.. scrape the roots gently on pavement.. and replant it ... i suspect something underground is weakening it ...

but it seems.. in your pic.. every leaf is out of focus.. so i am having a hard time.. find spots to focus on .. unless you are talking about whatever is eating the edges?????

in 20 years of hosta.. i have never heard of a fungus problem being PRIMARY .... that need be dealt with .... i think you are off track there ..

but that does not mean.. that a bug is not primary.. breaking the surface.. allowing a fungus to be secondary ... in other words .. you have to solve the bug/slug issue.. and then you wont have a fungus ... [and that is presuming rust is not a fungus]

ken