Hi Bill:
Yep, a tad early for trees to begin their display of fall colors. Granted, there are numerous blackgum (Nyssa sylvatica) trees here on campus that have 5-50 full red leaves as of July 8, but that's a unique feature to that particular species.
I'm going to suggest environmental stressors or possibly genetics. I wouldn't worry too much about it right now, unless of course, these trees start dropping all their leaves!