Change the location of your grows. Different plants use different nutrients from the soil. If you change the location every year, you will get bigger and healthier plants.
Make use of rain water. It is useless to give tap water to plants. You can easily collect rain water into a big container and water the plants with it when needed.
You can get excellent grows by using the seeds from the fruit you eat. For example avocados and mangos are easy to grow.