We had a lot of white druplet this year. Both Navaho and Triple Crown were significantly affected.
White druplet is caused by too much UV light. I read something this season that supposedly white druplet is not directly related to temperature, but is indirectly related to it.
In other words the (hot) temperature itself will not cause white druplet, but high temperatures are generally associated with low humidity, and the low humidity allows more UV exposure to the berries, which does cause white druplet. Apparently high humidity blocks a lot of the UV radiation which is harmful to blackberries.
One may ask, “If white druplet is caused by UV exposure, why then do I see it on berries which are inside the leaf canopy?”
The answer is that supposedly berries inside the leaf canopy are more sensitive to UV exposure, and thus just as susceptible to white druplet, even though they are more shaded.