There could be many reasons for the problems on show while growing Grapes, it can begin as early as when new buds begin to swell on the vine (even before then) as when we grow grapes here we wash all the BARE vines after early year pruning, this kills off any bugs hibernating over winter and also any diseases that were a problem from the previous years growth, Obviously there are products that you buy to spray at this time as everyone I know who has a vine or two, will never spray when the flowers or little fruits are forming.
As the fruit is forming and the plant is growing so much foliage, you also need to remove a lot of foliage to allow air to flow through the whole vine, you then have to use sharp scissors to thin some tiny tightly forming bunches as this also allows disease to form on some fruit that is tightly packed, by removing a small amount of fruits within the bunches allows the fruit to expand without bursting, choking each other out and when the fruit bursts insect love the sugery juice, this helps spread bugs diseases too.
If I were the owner I would go to the library or book store to read up on care and needs of a vine as some of my friends are actually 2nd - 3rd generation owners of such, one has the top of the vine growing inside a greenhouse while the root is on the outside, this was obviously done by breaking a hole through the wall at the base when the vine was first planted and the top growth fed inside the greenhouse, this also allows for manures, feeds ect to be added and as much water as a vine really requires, (a Lot of water) the other owners grow the vines in Large containers inside greenhouse, but they have to cut the roots each year when new top soil and feed is added, both methods give good results but, take up a lot of time caring, pruning and enjoying there fruits.
The middle picture you show is a RED grape type and not a brown disease. the first picture shows bunches too open in structure pos due to wrong watering, poor airflo at flowering time / Pollination, and the third Pic shows a white mould forming on foliage, cause is insufficient air, hence my suggestion cutting out a lot of foliage early summer to allow air to flow.
Hope some of this helps you out a bit, Grapes are not hard to grow once you master how to care for them and what could be nicer than cutting a bunch of grapes you grew yourself.
Good Luck, WeeNel.