Thank you for the question. I can’t tell you for sure what is wrong with your raspberry plants from the photo but from what I can see, it might be gray mold of raspberry. Raspberry flowers, canes and older leaves can be affected too. I can see in the photo that your plants may be crowded either by weeds or other grass like plants which may reduce the airflow around your raspberry plants. Gray mold development is encouraged by such crowded conditions that prevent your plants from drying out after rain or watering. We have had a cooler, wetter season so far this year which doesn’t help your problem. Here is a publication from the University of Minnesota's self diagnostic program called "What's Wrong with my plant?"

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

"The most effective way to reduce gray mold in raspberries is to reduce free water on leaves and blossoms. Choose a location with full sun and good air movement. Raspberries should be planted in narrow rows that dry quickly after dew, irrigation or rain. Use drip irrigation or soaker hose to keep leaves and blossoms dry. If sprinkler irrigation is the only option, water in the morning on a sunny day so plants dry quickly. Always remove dead floricanes to increase air movement within the row and thin new primocanes to maintain a narrow bed size.

Remove potential overwintering sites of the fungal pathogen by removing dead floricanes and pruning out any canes showing symptoms of gray mold on the cane. Infected canes should be composted well away from the raspberry patch in a compost pile that heats up. Alternatively, infected canes can be burned, buried, or brought to municipal composting facilities depending on local waste management regulations.

Gray mold pressure can be reduced by regularly harvesting the fruit and not allowing overripe and rotten berries to accumulate in the patch. Pick raspberries early in the day when fruit is still ripe. Take care not to bruise or damage fruit during harvest. Cool raspberries quickly after picking. Remove infected fruit from the patch to reduce spread of the fungal pathogen to developing blossoms and fruit.

If the patch has a history of gray mold, and there is a long wet spell during bloom, then fungicides are advisable. The best time to apply fungicides to prevent gray mold is during bloom, when the first infections can start. Fungicides can also be sprayed during picking, but they are less effective at this time. Several formulations of captan are labeled for gray mold in raspberries. Captan will prevent gray mold from infecting fruit but will not cure gray mold that has already started".