Yellowing leaves at the bottom of the plant (the older leaves) sometimes mean an iron deficiency. Pumpkins are big feeders so perhaps they at a lot when you were gone and you need to feed them some more! We’re not sure what you mean by the vine “darkening.” As the pumpkin reaches maturity, the vine is more likely to turn yellow. If the leaves start to wilt, look at the base of the plant and ensure you don’t have the squash vine borer. See more about identification and control: http://www.almanac.com/pest/squash-vine-borer
Yellowing leaves at the bottom of the plant (the older leaves) sometimes mean an iron deficiency. Pumpkins are big feeders so perhaps they at a lot when you were gone and you need to feed them some more! We’re not sure what you mean by the vine “darkening.” As the pumpkin reaches maturity, the vine is more likely to turn yellow. If the leaves start to wilt, look at the base of the plant and ensure you don’t have the squash vine borer. See more about identification and control: http://www.almanac.com/pest/squash-vine-borer