I suggest this regex to replace only those within the Description:
:
(?:Description:|(?!^)\G).*?[a-z]\K[A-Z]
And replace with $0
(?:Description:|(?!^)\G)
matches Description:
or at the end of the previous match.
\K
will 'reset' the match so you don't have to put back what you matched previously.
Since .
doesn't match newlines by default, you don't have to specify the ending \r\n
'keyword'.
The regex above works on N++ v6.5.2.