What is happening here?

[Ralphee]

G'day all!
New grower with an older vineyard here (22-24 year old vines, but i have just bought the property)
One half of the vineyard has gone like this (see photo) and i don't know why, hence i thought i would ask people wiser than myself!
Its Merlot grapes and this is one of the better looking bunches, the brix says its ready to be picked (or very close to it) but as you can see - its not worth picking!
Can anyone point out what i have done wrong here? (its always me that's done something wrong....lol)
Too much water? Not enough?
I sprayed every 3 weeks for mildew, made sure i had good coverage
The previous owner said this side wasn't as strong as the other side (the vineyard is in two sections) but this whole side has gone like this???
It wasn't a good year, late rain and then little sun, big bushfires causing smoke haze to block out the sun, but i kept the water up and we had enough for the other side to be okay.
Help?
Thanks

 

[salcoco]

I am not sure but it look like black rot. a fungus not detectable until grapes start to ripen. need to start spraying every two weeks beginning when growth is three inches. are there any other vineyards in area that you can discuss the disease with? it has been a while but I think Manzobed (spelling) is the required spray.

 

[NorCal]

If I were to take a stab, I’d say the result of powdery mildew.

 

[Xnke]

Powdery mildew or black rot. Mancozeb/manzate or Captan, are my go-tos.

 

[Ralphee]

Will be annoyed if its powdery mildew... I sprayed for that every 3 weeks!
Of the top of my head its the Captan i use, also have a sulfur one i did a few times too.
Roughly 110 vines with maybe a dozen decent bunches of grapes over the whole area....
Thanks everyone, i am more looking to make sure it doesn't happen next year as its much too late this year!