A couple possibilities come to mind that may or may not be helpful.

The first might sound silly, but are you sure the female flowers are getting pollinated? We have few pollinators in our area, and I've been hand pollinating this year. The success rate has gone through the roof, with even an uptick in zucchini setting on. Some would see that as insanity, of course :) And just in case you aren't already aware, Butternut (C. moschata) and Acorn (C. pepo) generally can't pollinate each other.

It's also possible the vines don't think they're established/mature enough to bear fruit yet.

Another possibility could be, as you noted, a watering or nutrient problem. Blossom end rot (BER) affects more than tomatoes, unfortunately. My understanding is that BER is caused by a calcium deficiency within the fruit, the root cause of which is uneven soil moisture. If the soil alternates between too dry one day and too wet the next, it might cause a problem with calcium uptake.

Along those lines, but perhaps not as common, is the possibility that the soil pH may be so high as to interfere with the availability of calcium. I've only read a bit about it, though, and don't know if it's yet another urban legend.

Anyway, those are my thoughts. With a little luck, one of the squash experts can chime in with more information.

I sure do envy your hoop house. Good luck!

Here is a link that might be useful: Hand pollination of Squash

Thanks for your help! Would I see any fruit production if the flowers were not getting pollinated? or would the female flowers just stay "flowers"? I'm seeing gourds (fruit?) start to develop,then die off....

Thanks!

Oh, yeah. Good question.

As I understand it, one way to tell if it's lack of pollination or BER is the size of the immature fruit when they die. And, yep, I've had both problems happening at the same time. If it's lack of pollination, the fruit just seem to sit there a while without seeming to grow much, if at all, before they wither away. When it's BER, the fruit have grown - sometimes quite a bit - before they suddenly stall out and go soft. I just had that happen last week with a lovely little Jarrahdale that was going great guns. It's so very sad :(

Hope that helps.

PS - I need to add the caveat that my experiences have to do with squash rather than gourds, as I've never grown gourds. If I've given you bad, bad information, hopefully a gourd expert will jump in soon to correct it!