You didn't give me much information.  What variety of hydrangeas are they?  Are they all the same?  What is the soil like in that area.  I see they are mulched with rocks.  How about sun/shade.  The corner one probably gets a decent amount of sun but those on either side of a door may be shaded.  Please respond with the information I need.  Thank you.

Thank you for replying back. They are Annabelle hydrangea. This is the third summer that we've lived in the house. They were here when we moved in and for the last two summers they have been fine. The house gets afternoon evening Sun in the front where the bushes are. We have Rock in the front. And if you have any other questions, please let me know. I'd love to get to the bottom of why it is so sick. I have attached some pictures. Thanks, Tom

I actually think two of your Annabelles look good.  Try pulling the rock mulch away from the base of your sickly shrub.  Work in some granular fertilizer and then some compost.  It is not happy with the growing situation and maybe that will help. Check to see what is different in that spot.  Perhaps does water pool?  Or, does it not get much water?  Is a gutter draining on top of it?  Don't overlook any possibility as to why that plant is suffering.  There has to be something different there as Annabelle is a sturdy, hardy hydrangea that can withstand neglect.

Thanks for your help. We have water that pools on the sidewalk  by the sick plant when there are heavy rains. Maybe it's getting too much water. Hopefully it can bounce back!