I just came across exactly the same thing on one of my sites. Now I know exactly what you have.
It is caused by one character or even a space that has somehow been converted to a special character.
I did a quick replace of a page of spaces, or maybe the characters and spaces, and that fixed it.
eg: I had these three characters together : <
in my edit page view it looks right, but when published it showed on my browser as :Â<
Replacing ": <" [copied and pasted from my page] with ": <" [typing the characters] fixed it.
Easy for one page, but I appear to have a whole site to fix !!
I may just download the plugin you are using ;)
No idea what made it change recently.