Micki,
When trees show their fall colors early it means the tree is stressed for some reason. It is common when trees are first planted or for the first season after planting due to the stress of the move from nursery to your home. However, with your tree being 4 years old that is probably not the case here. Unfortunately, I cannot tell what is stressing the tree without seeing it. My advice to you is to either cut a small branch off and take it to local nursery so they can run tests to see if the stress is new or old, or you can have an expert out to your house. Some common causes of stress are over watering, gurgling roots, disease, pests and relocation of the tree. Perhaps some of those will shed some light on your situation.