So, things are not going well in your garden and you aren't quite sure what to do. Maybe the plants aren't growing, or the fruits have problems, and production seems low. The first step towards a correct resolution involves pinpointing the exact problem, consisting of a bit of detective work.

Environmental Conditions 

How's the weather? Wet conditions, whether hot or cold, are very conducive to disease. Disease can be bacterial, fungal, or viral. Different diseases will require different solutions.

What's the date? Pests such as squash vine borers have a specific life cycle. (To avoid the problem, plant when the vine borer isn't laying eggs.) Get help with dates, garden planning and more at Seeds for Generations. 

It wouldn't hurt to test your soil pH because if the soil is too acidic or basic, the plant won't take up the nutrients. Commercial chemical tests are quick and easy. Be aware that these aren't as accurate as lab testing but will get you a good ballpark figure.