Answer: First, I'd cut way back on the watering. Too much water, or soil that remains soggy wet for extended periods of time, can actually suffocate the roots because the water drives out air and roots need air as well as moisture. One deep soaking each week is about all your grapevine will need. As for the affected leaves, if they are wilting and turning brown there is probably an injury to the vine. Follow it down to the base of the plant and look for damage - weed whacker damage, rodent chewing, insect holes, etc. If you can't find any physical reason for the odd behavior of your plant then it is showing distress from root problems. Adjust your watering and wait to see new growth. Once that happens you can cut away the affected plant parts to make room for the healthy new growth.
Best wishes with your grapevines!
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