Fret Buzz after tuning down and back up

[Bluesbreaker5]

Last night I jammed for about 2 hours with some blues musicians who asked me to tune to Eb, Ab, Db, Gb.

When I got home I tuned back to E, A, D, G and I had fret buzz everywhere, all strings, except the higher frets.

It's a Squier VM 4-String with Fender Tapewounds (which got alot of looks).

So why the fret buzz when I tuned back up a half-step?

Would tuning down for 2 hours cause that much change in the neck?

If so, and I decide to jam more with these guys, then how can I keep from fret buzz with both tunings?

Thanks for any help.

[JustOpenYourMind]

your neck has probably moved because flat tunings have less tension. try to adjust the trusse rod.