I'm growing 5 winter squashes in a 5'x24' well prepared bed. Everything has been going fabulously, plenty of set blossoms, an ocean of vines running everywhere. Until a week ago I noticed a single wrinkled fruit. It was clearly a goner so I picked it and sliced it open. It is shown below. Today I noticed another one that had a hole rotted thru near the blossom end. I snipped it off and opened it up. It smelled very foul inside. Now I've found that all of the larger fruits on the three Sweet Meat vines are rotting thru at the blossom end. They're very juicy inside and smell horrible. Further, there's lots of freshly set fruits that are slimy and rotting on the same day that they bloomed. There are nice, large fruitlets where blossom end is clearly infected and rotting thru to the insides of these fruits. I even found one rotting that hadn't even opened yet. On the other hand, there are some that look normal. Almost as if this infection is passing.

The two other squash vines intermingled in here appear uneffected. A Marina Chioggia, and a Galeux D'eysines appear to be fine. There's only a couple of fruits on each one, and they look great, but they're also growing at the oppossite end of the bed and mostly direct in a different direction. And one of them looks a tad suspicious and I'll keep my eye on it.

So... any ideas? What could cause the sudden demise of all of these squashes at all stages of development?

Could it be overwatering? Our soil drains quite well so I water every other day during warm weather. And this was happening before the current heat wave we're going thru right now.

The leaves look healthy, the vines look fine, they're rooted down everywhere. It's all good except all the fruits rot.