I didn't read all the posts - but I work in Cardiology and a "slight murmur" is usually nothing to worry about. (I have a murmur myself.)
Murmurs are graded I through VI -- with I being almost harmless and VI being the loudest and most serious.
If the murmur your pup has is "very slight" --- there is a good chance that it just wasn't heard during earlier examinations.
Run a search on YT - "Murmurs". This topic has been discussed many times. And, I, myself, have posted a lot of information about murmurs here on YT.
Also - there is a lot of information on the Internet regarding murmurs in people and in dogs.
I doubt you have anything serious to worry about - but do keep in touch.
Carol Jean |