If the spray used for the weeds on the hill was 2,4-D or dicamba, it could be the problem. It looks like chemical damage. 2,4-D is a growth regulator and your vines look like they tried to open a million buds. Grapes are very sensitive to 2,4-D for one thing. For another thing, you can spray when the wind is still or blowing away from your grapes and the next day if there are certain atmospheric conditions, the 2,4-D will form a vapor that rises up and drifts. It has been known to drift for a mile. Time will only tell if your vines will come out of this. Assuming replacement would occur over the winter, you could at least give them until then to see how they do. I've had muscadines (granted, they have some differences from vinifera grapes) get the leaves killed crispy brown and I cut back finger thickness wood, thinking it would make it easier to dig them up later. I got busy and didn't get the "dead" one pulled up before spring and it budded and leafed out a foot off the ground. You just never know.
