I don't know anything about the Chinese elements, so there's been no deliberate attempt to mimic how they work! That's interesting though, if you see connections there.

I wouldn't say that all elements are used in everything in this setting; if anything they're comparable to the real elements on the periodic table, which all things are made up of, but not every thing contains them all. I suppose things would be 'of an element' if they're made up primarily of that element, whereas anything made up of a mix would register as 'non-elemental'? So a standard sword probably would contain all of them!

And it's good sign for what I'm doing with the lore if you're interested in finding out more about it!