I though this was 'black rot'. My grapes look like this even when I spray although I'm going to have to rethink my approach. I'm not sure where you live but the link below is the resource I have used to research fruit spray schedules (including grapes).

Here is a link that might be useful: Midwest Small Fruit and Grape Spray Guide

now that i looked at more pics i think youre right on the black rot thanks

I used to get control of that and all other important fungal issues with grapes with Immunox as a single spray about 10-14 days after last apples lose petals of flowers. I now have a variety where that timing or number doesn't work and I intend to follow up with one more spray next year 10-14 days later still. Or I might try just that subsequent spray to find out if it was only a matter of timing for this variety.

I liked the previous timing because I'm spraying then anyway. I'm confident that Funginex (myclobutanil) is your best bet as a compound to control bunch rot (or whatever rot) although I think it can also be done with the more persistent application of sulfur. It is a crop that is grown organically in the northeast by some commercial growers.

The infection begins when the berries are very tiny. As they get larger the skin gets tougher and more resistant.

Immunox can also rescue an infected crop, but can't erase the black spots.

I picked up some Immunox and sprayed my remaining grapes with the hope that I can save some. While I was at it, I sprayed my 4 gooseberry plants that had been nearly defoliated by a fungus and several trailing blackberries that had leaf spot. It's been a tough year for fungus on plants.