Most hydrangeas in the Twin Cities area have responded beautifully to the abundant rain, so rain itself probably doesn't account for the plant's condition.  However, if it's rooted in a spot that isn't well-drained, too much water could be a factor.

Was the plant that's growing well moved at the same time?  If so, it's difficult to explain the disparity.  

It often takes established plants two or more years to adjust to a move.  Following is information about transplant shock and its effects.

https://plantpathology.ca.uky.edu/files/ppfs-or-w-19.pdf   

Thank you your answer. The problem with your argument about drainage and water is that the plant next to it was moved at the same time. 

Although we can't see much detail, the plant in the photo appears to be stunted, but without dieback or wilting.

Wilt is usually associated with too much or too little water.

What the roots look like is another matter.  Root disease or nematodes could be at work.  After onsite inspection a tree/shrub care specialist (certified arborist) might be able to diagnose the problem.

Fertilizer isn't likely to benefit the plant until it begins to recover from whatever is ailing it.  

As for advice-- The plant still has potential. Consider how much you value it.  Then continue to provide the best care you can and patiently wait to see how it fares. (Asking an arborist to assess the plant's health is a "best care" practice.)

Following is a reply to a similar question:

https://www.torontomastergardeners.ca/askagardener/annabelle-hydrangea-has-stunted-growth/