One way to help find all references to a source would be to download your tree to a gedcom file (tree pages - tree settings - export then download). Near the bottom you'll see something like:
0 @S-xxxxxxxxx@ SOUR
1 REPO @R-yyyyyyyyy@
1 TITL North Carolina, Death Collection, 1908-2004
1 AUTH Ancestry.com
Find the SOUR id ( the @S-xxxxxxxxx@) of source you are interested in then search for all references to the source.
0 @Pxxx@ INDI lines are the start of an individual. Note the name, birth, death info of individuals with a reference to your source. Using that info go to your online tree and manually remove/fix the citations.