Depends on when you planted them. My bottle/swan/birdhouse gourds have fruits as big as 6-8 inches plus younger ones.
Maybe you should pinch off the tip of mains, to grow more latterals. The latterals are supposed to have more fem. flowers.
They don't produce as many fem. flowers if not enough sun.

It is good practice to prevent diseases than fight them.
I do too use neem oil spray on my cucurbitas.

mildew is the number one cucurbita vine killer. The mildew fungus is air born and that is how you get them on your plants. If the environment is not favorable(sprayed), they cannot multiply.
That is the wisdom of spraying regularly.