Hallmark 60's Custom, fret buzz after string change?

[Hydra19]

hi, i have a bit of an issue with my Hallmark and I'm not sure what caused it. I changed the strings from 10's to 9'a and since then it seems like there's a bit of fret buzz on the treble strings, up to the 5th fret, around 3-4 mostly, after a barrre A chord it's fine. So why the buzz? Is it the lower tension of the srings? Should I put some relief into the neck to compensate?

Also, when trying to set the intonation on the treble E string, the saddle is all the way forward, and the 12note is still flat. When I play the harmonic it's in tune, but not when I fret the note on the 12th fret, it's a couple steps too flat, and I can't adjust the saddle anymore foward.

I haven't noticed this problem before, and have set intonation on this guitar before.
The strings were changed 2 months ago and I didn't really take any steps to fix it properly. So it could be time for a string change? It has also gotten very cold here in the last month, don't know if that has something to do with it.

All help much appreciated, the guitar still sounds good and gets played!

[Bob Shade]

First, try looking down the edge of the fingerboard from the headstock toward the pickup and see if the neck is straight or needs an adjustment.

Second, the bridge may need to be adjusted up very slightly to compensate for the lighter strings. The lighter the string, the more it vibrates.

Third, the intonation issue is likely a bad string. Try a new one and stretch it out good when tuning until it stays in pitch after you pull it out.

Best, Bob