Just to lead on from Christian's questions....
Assume that it is colder temps that are causing or contributing to the appearance of the pathogen and subsequent leaf damage. IF the temps were low enough to have caused the plant to weaken to a degree that allowed the pathogen to cause this damage, wouldn't you expect to see other sings of the plant not responding well to the lower temps such as: slow or no growth, poor pitcher development, etc?
In my particular case and at this stage I'm not attributing low temps to the issue, as this pathogen does appear about equally on both LL and HL plants.
LL - N. truncata x vent and Merriliana
HL - N. sanguinea and N. fusca