If you have pollinated more then one pumpkin on your plant it is important to select your chosen one and cut off (cull) all others. This will give your plant the best chance at producing a winner. When culling there are a few things to consider to help you select 'the one'.
1. Maine vine vs. side vine: Just about all the winners come off the main vine so favor any you have set on the main
2. Pollination date: The ideal window is July 1st to July 7th but it can be difficult to hit this small time frame, but if you have one in this prime zone this is a plus
3. Distance out: A pumpkin that is set to close to the initial plant site could give you problems later in the season. Use 8ft. as the absolute minimum and 12ft. - 17ft. as the ideal range. By having a pumpkin further out this gives the plant more leaves behind it to push nutrients and water to your selected pumpkin
4. The hard choice two pumpkins on the main vine, one is only 9ft. out and was pollinated on July 2nd and the other is 14ft. out and pollinated on July 6th, which one do you chose? I was faced with this exact situation this year and I had to go with my gut feeling, and I selected the smaller one that was further out in hopes that later in the season having more vines behind the pumpkin will keep the pumpkin growing up to the weigh-off day.
Pumpkin sun protection:
It is important to keep your pumpkins stretching skin as flexible as possible and letting the sun directly shine on it will cause sun burn and ultimate cracking. So get an old white sheet and just cover your growing pumpkin. Color is important, some people have used black and this has lead to damage to their pumpkin, white allows some sun to get through but not enough to sun burn the pumpkin
Cut those tap roots:
You may have noticed that under the leaf stalks there are roots forming. It is important to cut these roots that are near the pumpkin or the pumpkin will actual tear itself off the vine as it grows.
Try and slowly get your pumpkin at 90 degrees to the vine. This is done by slowly moving the pumpkin a little each day. Some people base their pumpkin on its position when culling but I have been able to correct some angles that were less then ideal by a little nudge everyday.
Keep up with your milk, fungicide, and insecticide sprays. It is around this time of year that insects often spread diseases like bacterial wilt and mosaic virus. Also, for fertilizers consider using kelp / seaweed, since it is high in potassium which helps grow pumpkin meat.
If you have any questions let us know so we can hopeful diagnose your problem before it becomes out of control.
Best of luck and we look forward to seeing you at Durham this year!!!