I suggest that you check the soil, it appears it lacks iron.

Just place a rust old nails, dig in the soil 3 inches deep

1 feet away from the plant. Try it. It should work

B. Shah

I hope you didn't give up on your Luffa plants. We have been growing them here all year as well and ours didn't flower until mid-July/August and we didn't start finding fruit until this month! It has a loooooong growing season but it works out when the weather cools off.