[mdjlucan]

The leaves are still yellow I gave them plenty of water and fertiliser They’re in full sun just don't know what's going on with them

[jambop]

At the risk of everything I know... These vines are not short of water or nutrients. What they need is to be properly pruned this winter. In short you are growing far too much from a weedy spindly plant. You say that these vines are some three years in the ground. I would expect them to be much more robust vine by now with a main trunk of about somewhere near two or more centimetres diameter. The last time you posted about these vines I suggested two possible methods of pruning, cordon or Guyot I stick with that.
 If those were my plants I would dig them out when dormant this winter and replant them with a one meter spacing between them. They are too close together they should be about one meter apart. I would prune them back to leave a few buds on the main stem and then after they have grown on next year in the winter when the plants are dormant choose one of the new shoots as either a permanent cordon or single Guyot prune the plants. You have to appreciate that these plants are growing in conditions which are not the most favorable so do not ask them to do so much. Also when planting out make sure you ensure there is good drainage around the foot of the plants. Good luck with that.

[mdjlucan]

Is this why the leaves are gone yellow

[jambop]

Is this why the leaves are gone yellow

It could be leaves do have a finite life on the vine and some do die off. The way I am seeing it is that you are asking the plant to support all that top growth through what I suspect is a weak root system. The roots can only supply so much after that limit has been reached it is natural that something has to give.
However there could be a problem with root pests and what you could do, again when the plants are dormant, is dig them out and inspect the roots make sure nothing is munching them. Vines are as tough as boots so you can replant them no problem. I notice the are up against a lawn ... do you ever put any treatments on the lawn? If you do this will affect the vines.
In short, and I repeat, I would dig the vines out in the winter and replant them in a good sized planting hole which has been enriched with some compost and long lasting fertilizers. After the first year of regrowing either cordon train or Guyot prune. Cordon is a good method because you leave a single cane with say seven buds on it wrapped around a wire. These buds will each produce a new cane which will bear a bunch of grapes. At the end of the season you simply prune each of the canes on the cordon back to create a spur with two buds. These should re-grow two new canes in the spring , once they are growing well and the threat of frost is past remove the cane furthest away from the cordon on each spur. Only leave the one furthest away if the one nearest is obviously very weak. This way you will only get seven bunches of grapes but they should be good sized and ripen well. Repeat every year
Here is a good video to follow about planting your vines it is in French but easy to follow the drainage holes are only really required if you have a hard clay subsoil.

 Plantation d'une vigne. Raisin de table (variétés résistantes aux maladies). - YouTube

[mrs bouquet]

There are lots of things that could be causing it.    I have a vine that is 200 feet long.     If you look at google "problems with vine leaves", there are lots of 'photo, that will help you identify what is causing the problem, along with how to deal with it.   Good luck,  Mrs Bouquet

[jambop]

There are lots of things that could be causing it.    I have a vine that is 200 feet long.     If you look at google "problems with vine leaves", there are lots of 'photo, that will help you identify what is causing the problem, along with how to deal with it.   Good luck,  Mrs Bouquet

Offttt! That must be a total nightmare to prune Mrs Bouquet a healthy vine with one bud every 6 inches or so  400 canes per year  On the up side you do have a 70 vine vineyard on one plant!

I do know of a vine down here that grows on the side of a house that must be about 30 or 40ft... actually gives the owner some nice grapes from time to time... nightmare to prune he has to do it off a ladder.

[jambop]

For those who are interested in the culture of grapes we will remember back in early June there was debate about whether grapes need much by way of water through the year. I posted some photos of my vines at the time and stated that there is little or no need to water grape vines they know how to get the water they need. here are some photos I have just taken today of my vines more than two months on from then. During that time we have had almost no rain at all if we have had more than a few millimetres that would be it. I have lopped back about 5 or 6 hundred mil of growth from the top and to be fair the needed doing again but I have netting up and could not be bothered taking it down to do so the grapes will be a little bit smaller than they would have been. I removed a few bunches of grapes as well so they would be a better size.
I think we can see from the pictures that grapes will do OK without water. I could have watered these and just maybe got more grapes and possible bigger. The sacrifice is that they would probably not be a sweet as these are and crucially you need the weather to get them ripe so in a poor year the flavour suffers. These are grown against a south facing wall and are ahead of grapes that would be grown out in the open ground. Of course all grape growers would like to shelter their vines from harsh north and east winds it is just not always possible but if you can it is worth the effort.
It has been a consistently hot and dry summer down here in SW France six or seven more weeks of this and it could be a great year for wine from this region... not my garden though