Good Morning, 

Thank you for contacting the U of M Extension Service. 

Please click on the following link about pruning hydrangeas: https://extension.umn.edu/planting-and-growing-guides/pruning-hydrangeas-best-bloom

Here is another link about leaf spot diseases of trees and shrubs: https://extension.umn.edu/plant-diseases/leaf-spot-diseases-trees-and-shrubs#causes-of-leaf-spots-1156260

If you scroll through this information, it discusses different types of leaf spot diseases and management of the disease. With the cool and wet weather we've had this spring, there are lots of fungal diseases appearing in the garden. 

We do not endorse any particular nursery or horticultural retail store. I looked up the Berry White Hydrangea, and it is a First Editions for Bailey's Nursery. This is a link to their website about your shrub: https://firsteditionsplants.com/resource/rockstarplant-berry-white-panicle-hydrangea/

This information indicates you should not prune this shrub until late winter. The "rogue" shoots might be the shrub starting to get larger. 

You did not indicate how the soil is, or if the shrub is in a rock landscape or wood mulch. Wood mulch, a few inches thick, a few inches away from the stem of the plant, will keep the soil moist, cool and protect the roots. If there are rocks or landscape fabric up against the stem of the plant, move them away and allow good air circulation around the plant. 

I would not prune the rogue stems until late winter. If some of the leaves die due to the fungus, pull them off as stated in the management section of the leaf spot disease link. 

Good Luck!