Have you checked the moisture around your plant? I would stick my hose right down into the root ball and soak the root ball. Check to see how the water drains, it should disappear quickly. For this baby plant I'd get a chunk of shade screen and tack it to the fence above this plant, drape it over the plant during this hot hot weather. You can roll it up when the weather cools down a bit. Hoe the weeds off and dump decomposed compost on the soil. That will keep the roots cooler, moisture more regular.
A little fertilizer is necessary for all plants. Osmocote 14-14-14 would work nicely. It is extended release so it is allowing a little N, P and K to be available to your plant, not too much and lasts for 6 months. Do half of what the directions tell you. Where fertilizer is concerned, 'Less is Best, More is Death and None is Dumb'. My dumb ditty but important to remember.
Fertilizer is not 'food' for plants, plants make their own food via photosynthesis. All those grapes take some major photosynthesis happening to produce all of those leaves and fruit and if those chemicals plants need for their photosynthesis factories (chlorophyll) are not available in the soil the plant's factories shut down (yellow). If there isn't the correct amount of NPK plus minuscule amounts of a dozen other chemicals on the periodic table plants will die slowly. Add a little too much and those plants will die very quickly.
Water, shade and a little balanced fertilizer should revive this plant. Compost is a great weed suppressor/killer. Compost if decomposed will be then available to the macro and micro soil organisms for energy, food. They eat then go back into the soil (only the top 6" of soil has enough air) and poop it out mixing the organic material into your soil. All soil is good soil, even (gag me) caliche clay. You need to get to know your soil and the best management practices for your soil.
The bottom of your fence looks too close to the soil and plants. There should be a minimum of two inches below that bottom rail of your fence and the surface of the soil, mulch...rocks. I hope I am on the right track making assumptions here and that this makes sense.