Hi there.
Here's my issue:
I own a Ibanez 6 string (506) and put a set of DR strings on it instead of the original Elixirs. Until then, the setup of the bass was fine. After changing the strings, the high C and G started snarling (fret buzz) at the 1st fret. I set the saddle higher but no relief... Here on TB I was told that the tension of the DR's was not as high as the Elixir's. Ok, fine. Bought a set of Elixir's, the same gauge and type as the first ones. But now, the high C, G and D are snarling at the 1st fret

Didn't adjust the truss rod at all, and put the saddle back to it's original position.... What happened?
No, no temp changes, moisture etc.