A dumped some composted manure on top of the ground 1 month after planting (it was an afterthought). I also add some Fox Farm Big Bloom every 3 weeks.

Might just need more watering, as pumpkins need a lot of water! Someone already mentioned it could be malnourished! Just google to see what kind of plant food is best for pumpkins. I try to grow some every now and then and it always seems like they grow ok for a while, then end up rotting out on me! I may try something different w/ pumpkins if I try them in the future. I would love to grow some nice, biggies! I am growing mini pumpkins this yr. I need to give them some sort of plant food, myself!

looks to me like drought stress and iron deficiency.

It's getting full sun, right?

I second the above question, how much sun are they getting? Could be a ph issue with your soil too... How close to the water are you, being on long island? The salt spray from the ocean can make gardening a challenge...

Direct sunlight for 7 hours a day. Not near any shores.