It's generally a distribution issue. Do the grounds clump out of your grinder? If they are clumped when you tamp, you'll get nasty channelling. A difference in humidity and temp from the move could require a different distribution technique.
I generally updose the PF so it's highly mounded. I perform a modified Stockfleths circular sweep, then sweep the mound off NSEW, tamp, pull shot.
As far as water, buy some Fiji just to see how it changes the taste, and modify your water supply from there.