Please send more photos. Show the whole tree, from soil to tip-top. Also, pull back a piece a little bit to examine for insects. What do you see? 
The University of Maryland Extension Service has this information, “Key to common problems of dogwoods”. Perhaps with more pictures we will see that your tree matches one of these. 

I’ll refer this to another expert. Often “wait and see” is an answer we give with young trees. You have so many, though, that a better answer is warranted if we can. A response may take a few days, as we’ve hit the weekend.
If we can’t offer firm advice using photos, hiring a certified arborist (See tips) to make a diagnosis is recommended for high-value trees, because they can make a site visit.

Your young trees look like they have been bashed into a lot. One of the images shows the canopy and that looks fine. Other wise the images show various wounds on the trunk from mid-way up the trunk to the bottom near the soil. The wounds have callus overgrowth where the tree has been trying to heal itself. Some of the wounds occurred one or two years ago and some are more current. I also see a porta-potty in the background. I suspect there has been construction in one of the houses and that activity may be the reason for the wounds. We try to protect trees from getting bashed into when a construction site is nearby.
Keep the wounded areas dry and free of dirt. The tree will try to heal itself without help from you. You are doing the right thing by keeping it watered and maybe a bit of fertilizer next spring will help as well. Good luck.