It is difficult to identify what is going on by the photos. Some of that is due to the time of year. What is visible is that it appears the shoots are showing some kind of water stress. The drying, drooping leaves would initially lead me to think the shoots got broken off the vine. But, since you say they haven't, I am guessing they are either not getting the water they need or the water is not making it up into the vine. 

If it is a water availability issue, I would check that any irrigation or water management you should have in place still there and functional. 

If water availability is not the issue, it might be a grapevine trunk disease. One common one is called eutypa. This is sometimes called dead arm or eutypa dieback because it can cause one side of a grapevine to mysteriously die. There are some other similar trunk diseases that can cause similar symptoms. The exact cause would not be important. if it is a trunk disease, the pathogen is blocking the vine's ability to move water and nutrients through the plant, causing the death of part or all of the vine. See if something like this matches what you are seeing: https://grapes.extension.org/eutypa-dieback-or-dead-arm-of-grapes/