There are several viruses and aster yellows that are known to infect hydrangeas in MN. In order to determine which pathogen is causing the problem, you would need to submit a sample to the UMN Plant Disease Clinic (https://pdc.umn.edu). It is unlikely that poor soil nutrition or low light caused these symptoms. Malformed flowers and unusual growth can occur with both virus and aster yellows infections. The recommendation for management of these diseases is the same, remove the infected plants and compost all plant material. Purchase a healthy plant from a reputable nursery as a replacement. You should decide if it is worth the cost of the diagnosis to know what the problem is before you removes the hydrangea. The following sites have more information:

https://www.tnstate.edu/extension/documents/Foliar%20diseases%20of%20Hydrangea%20FBG%20022916%20G1.pdf

https://extension.umn.edu/plant-diseases/aster-yellows