I checked your account history and I see we did make replacements. We replaced three for you in 2013, and another one in May of 2014 (as a courtesy at that time.) You bought these in October of 2012.
However, the manufacturing quality issues were sudden enough that it was quickly obvious in the printer. Most of the failures were immediate or within just a few days.
I believe what you are experiencing now is just normal life expectancy for this particular product. As I said, I do not think the other six are going to suddenly croak but they will continue to age and end their life peacefully as this one did. If you would like to replace this one and the other six remaining cartridges with the newest models, we can offer you a sweet upgrade price - but they have a 90 day warranty period like all of our products do.