We planted 3 pumpkins in a new patch this year, one of them is doing really well and has huge, dinner plate sized leaves. The other two had slightly smaller leaves, but were still very healthy looking. Two days ago one of them just shriveled up and died. I went over to look at it and it was like.. cut off at the dirt. Now this morning I see the other is on it's way out as well. It's flopped over, but is still attached to it's roots. What is going on here?