Apologies. I must have missed this one.
Create a cleaner and add an action like this:
^ - anchor match to the start of the line (with m option)
(.*?:\s+) - match & capture any characters (.*?) up until the colon (:) followed by one or more whitespace (\s+)
note: if there are cases of no spaces after the colon, change it to \s*
(\w) - match & capture the next word character
The parens ( ) within the expression capture the parts of the match that you'll use later. In this case, we have two.
In the replacement, we use a transform option to uppercase the next letter ($u)
$1$u$2 - replace with first capture group, indicate the next character is uppercase, then the next capture group