Over the last few days, I managed to lower the temps in the tent but not much. It went from an average of 26-27 C lights on to 24-25 C lights ON. That seemed to help to a small degree. The wilting started a little later and wasnt quite as severe - but not a lot of improvement.
So, starting last night I added a humidity dome and put some glasses of water inside it. The average humidity went from the 27% to 30% range up to 35-39%.
That seems to also have helped even more. Tonight there is still wilting going on, but its not as bad, and it seems to have started later in the evening. Its now 11:30 PM and it looks like it usually does at around 8:30 PM.
Im not sure how Im going to get the humidity any higher unless I build a serious humidifier.
So, this seems to be at least partly due to stress - mainly low humidity. Since I have nit seen this in any of the plants in my earlier grows, Im thinking that its also at least partly genetics in the form of less tolerance for low humidity. All my other grows were in the same tent with the same lights and the same humidity ranges.
I will up-date again in another few days and let you know how it is going. This was a good learning experience.
Thanks to all who contributed!!!