I've been trying to find two short stories that I read years ago, so far with little success. AFAIR they were both in paperback anthologies published around the mid-1960s:
1. The first is set in the world as we know it, but someone discovers that our universe is shrinking. No one noticies anything because of course everything is shrinking at the same pace - except the speed of light, so by the end of the story everything takes on a red-shift and eventually vanishes altogether.