You should always take the bottle back to the retailer. Total Wine has a 100% satisfaction guarantee and they will replace the bottle. It is highly unlikely that a good Cru Bourgoeis property like Tour St Joseph has "turned". It is likely at or near its peak for drinking, though. The 1996 vintage was an excellent Bdx vintage that offered plenty of cellar potential. The bottle that you have likely was mis-handled and/or exposed to heat during its journey to the US.