Zucchini Question?

Question:I have 3 plants and the leaves are shrivled and not healthy looking. I have other plants in my garden, and they are doing very well. Its just the zucchini that are struggling.
They get sun almost all day and are watered regularly. I'm assuming the soil is fine due to the quality of my tomato, eggplant and cuccumber plants that are in the same vicinity.
Any advice?

Answers:
Sounds like a borer bug,it eats the stem of the plant from the inside; it bores its way into the base of the plant, I had this problem and usually when the leaves start to shrivel its to late,
you can cut one of the branches of a plant and slice it open and you may see a bug that looks like a grub worm white in color if you do your plant will probably die.