Blogger tags

Well, obviously, the way to change all tags is to select them on each and every post where they are used, delete and then reinstate with the new spelling or format, in this case all lowercase. This might not work if there are a lot of posts!
On the other hand it is gratifying to notice that if a label is not used, i.e. the title case version, it does not appear in the show all labels, yes, tags are labels here, of course, and the philosophy behind them is a bit different to other tag usages.