My minor suggestion would be
Code:
Find: (<h[1-9]>)([A-Z])([A-Z| ]+)
Replace: \1\2\L\3
The big differences are including the <h tag, and allowing multiple words in the rest of the title by adding the space.
Additional punctuation symbols could be added by adding them to the [A-Z| ] grouping; ie [A-Z| |,|;] etc