Without a photo and knowing what variety of plants, it is impossible to tell what happened with your plants.  Be aware that some plants have red leaves when they first leaf out but the leaves turn green as they mature.  The first thing you need to do is take a soil test.  Indicate it is for a vegetable garden.  Then follow directions.  Here is the link: Welcome to the Soil Testing Laboratory | Soil Testing Laboratory (umn.edu)

Also, sandy soil needs organic matter added to help retain water.  Tilling in several inches of compost prior to planting will help.