Dig around it and check soil conditions, amended planting hole dug out of damp clay soil may be collecting water - when doing any future plantings do not amend planting hole back-fill.

What's your weather been like? Dogwoods typically respond to hot, sunny weather by curling their leaves and hanging them straight down. These are woodland understory trees and typically will show some heat stress in full sun. But I would also check out the soil conditions as Embothrium suggested.

was there any cold event back at planting time ... if minor.. it could have had a slight impact that is just now showing.. plus what they said ...

as long as it has green leaves.. it is not time to give up ...

i would remove the tag and nail it to the garage wall or some such.. might whip around in wind and do some damage ... i presume you want to keep it for warranty reasons ...

ken

check this out ... proper watering.. dealing with clay soil.. timing.. etc ... : https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

Thanks all. The TN site was very helpful... I think I made several mistakes, particularly too much water. I'm going to try and let it dry out and monitor the water as is described. Probably didn't do it a favor by planting in full sun, but went with the label instructions.