I had a similar experience.
I had bought our girls a bag of food a few months back and after I opened it I could smell a difference. I still fed it to the dogs... they ate it, but not w/o sniffing a bit first. They usually gobble it up. I took a look at the bag and dates were fine, but near the bottom of the bag was a small hole
... small enough to only see when looking for it, but not big enough for any food to fall out. I think this was the problem... the bags are vaccum sealed for freshness and the hole took away the freshness. I exchanged the bag for another and could tell the new bag had no problems.
I just wanted to let you know that this could have been what happened to your bag also, and that its by chance you grabbed that one bag, like I did. Fortunatly, there is nothing wrong with the food... just not fresh anymore.
