Hello, 

Thanks for reaching out! I am sorry to read about your currant bushes. To start, the UMN Extension has a great article about growing currants in your garden - there may be some helpful information here: https://extension.umn.edu/fruit/growing-currants-and-gooseberries-home-garden

Photos of the leaves may be helpful in assessing your problem further. Did you notice any particular characteristics about the berries that fell off? Did they have any holes in them, or did they look a certain color? 

Here's another helpful link: https://yardandgarden.extension.iastate.edu/how-to/growing-currants-and-gooseberries-home-garden