Just from what I'm seeing here....
Early morning, when somewhat cool, all the plants look well watered with the leaves standing out. As the day heats up, the leaves droop to the point that the plant looks dead (I assume they are trying to reduce moisture loss). Once the sun goes down, the leaves rise back up and look good again (unless the actually need water).
That's why I try to do the watering in the mornings, as if they are droopy then, they are thirsty and not just hot.
If they look particularly bad after sundown, I may give them a bit to perk them up a bit, but I try not to leave them damp overnight...