As far as I can tell, your columns didn’t have any content that was in all caps, so I couldn’t determine whether the String Manipulation nodes were doing anything. In any case, I cleaned it up a little and used the Column Expressions node for capitalizing the column contents.
I then branched off and extracted the column headers so that I could adjust their capitalization. After some manipulation, these fixed headers can be re-inserted.
Let me know if you have any questions.