Open string buzz?

Samuel

My guitar seems to be getting more fret buzzing lately, most obviously when I'm tuning or something and playing open strings. It was also getting buzzy at the 12th fret before I changed strings, and that might have gone away a bit...but it's still buzzing on open strings.

Is this something a truss rod adjustment might help? Or is it strictly a nut/bridge issue? Or is this just something that happens when you play louder and I didn't notice it before for some odd reason

also, it has been getting less humid lately, but it's still in the low 40's at the lowest, usually. So I don't think it's a humidity problem

Thanks for any help