What sort of budget are we talking here? Your gear list suggests it's not much of a concern, but ...
I'd say to take a critical look at your photos, and evaluate days out in the field critically ... do you feel like what you have is either too long or too short for what you want?
A 50mm is never a bad bet, and Canon has excellent ones, both with and without the ring ...
As-is, though, you have a fantastic lineup and you seem to use it quite well. If I were in your shoes, I'd be happy with what I've got.
Some clicking occurred, a few lenses were involved, that's about all I know ...