Sunscald may be responsible for the damage to the drupelets/fruits.  Sunscald is a physiological disorder caused by sun exposure (solar injury) and excessive temperatures.  Berries with full exposure to direct afternoon sun are most susceptible to sunscald.  However, high temperatures also appear to be involved as berries shaded by the leaf canopy may also be damaged. Watering the raspberry planting on a weekly basis (in hot, dry weather) may reduce the incidence of sunscald.

A fruit rot (such as gray mold) is another possibility.  Information on gray mold can be found at the following website. 

http://www.extension.umn.edu/garden/yard-garden/fruit/integrated-pest-management-for-home-raspberry-growers/gray-mold/