Native pink dogwood - Cronus rubric in New Jersey. Tree planted in May when ten feet tall. We've had a lot of rain, but have watered it well during dry periods.
Red Leaves in July
Certified GKH Gardening Expert
I think the damp conditions are the issue with your Dogwood. I see signs of fungus damage on the leaves in the picture.
You may want to contact the garden center you purchased the tree from to see if they would replace the plant.
Here is a link with more information.