Buy the 2015 Old Farmer's Almanac!
Some pumpkins just ripenSome pumpkins just ripen faster than others and it could be related to their location on the vine, how much sun they're getting, and other factors. Unless frost is coming, just let those immature pumpkins ripen on the vine; cut any leaves back to give them plenty of the remaining sunlight.

2015 Garden Calendar2015 Weather Watcher's Calendar2015 Recipes Calendar2015 Engagement Calendar 2015 Everyday Calendar2015 Country CalendarNew Year Cross StitchLobster Rope Doormats