Sounds like your guitar is taking on water. If
you keep it unprotected in a damp enviornment it will
cause the wood to swell, which may cause some movement.
This may explain why your strings are now buzzing. To
dry a climate can have ill effects too. When I have
seen guitars exposed to excessive moisture there is
often a dampening (dulling)of the tone of the guitar as
well. Try keeping it in a heated room and see if it
drying it out changes the tone, or alliviates some of
the buzzing. Using a different gauge string could be
a factor in the buzzing too. Good luck.