Dear Jdawn,

There is a disease that causes cupping but it is also associated with galls on the backs of the leaves.  I cannot see any galls. It is called grape phylloxera.  I am adding a link that shows the disease as well as herbicide injury to grapes.  However please keep in mind that plants become distorted in many ways with herbicide damage.

https://apps.extension.umn.edu/garden/diagnose/plant/fruit/grape/leavesdistorted.html

I am wondering if this grape vine is at the end of the row.  I suspect it has been hit with a volatized herbicide.  The days have been hot and if someone is using an herbicide it could change into a gas and drift over your plant.  That might explain why only one plant is showing these signs and only on some of the leaves.  The leaves curl and the grape clusters lose grapes where the gas hit the plant.

https://psuwineandgrapes.wordpress.com/2017/07/28/growth-regulator-herbicides-negatively-affect-grapevine-development-identification-of-herbicide-drift-damage-how-to-prevent-it-and-what-to-do-if-it-occurs-in-your-vineyard/

Lastly a publication from Oregon State on grape damage and disease.  Please check out pages 1 and 2 and the pictures (grape clusters) and see if that matches your grapes.  

https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em8975.pdf

Since your other grapes do not show any damage, I doubt it is a mineral, pest or disease issue.  

If you have further questions, please contact us again.