Seconding the bad news, I also have to say we're looking at:
(a) it had a bad day and dried out. If this is unlikely because there were no hiccups with the watering of this plant, then we go to
(b) root rot.
What tells me this is the pitcher color at death. If they're brownish, then it means your leaves died slowly (a more normal way for leaves to senesce). Since yours are greenish, it means they died very quickly. The leaves dried out suddenly from a quick and sudden stress, either a skipped watering or a pathogen (which often will cut off water to the leaves by killing roots). The plant did not have time to reallocate the valuable nutrients in those leaves. All the chlorophyll and other good stuff got left behind, which colors them a pale gray-green at death.
What is your media mix for this plant?