If the leaves are spotting and falling off it could be a fungal disease.
Most of the time these are the issues when planting vines
1. It doesn't get enough water. Vines are usually on fences, pergolas and usually are not watered regularly.
2. Vines are out of control.Vines need to be pruned to keep them on the trellis and the seedlings have to be weeded out or it just is a weed that will climb over trees, sprawl on the ground or even onto the roof. dead leaves and vines should be pruned out and fallen leaves picked up.
3. Vines planted on wall. Stone or concrete walls get very hot and air circulation and light may be a problem up close to a wall.
4. Roaches, ants, slugs like to hide in the vines.
5. If the vines are not thinned they can get very thick and wiry. Dead branches and leaves accumulate attracting the above mentioned critters but also provide an environment that promotes disease when the vines get wet from rain or overhead watering, especially if the vines are on a solid wall where the air cannot circulate very well. to help with air circulation. Build a trellis about 18 inches in front of the wall so air can get around the back of the vine too or plant a vine like creeping fig that sits flat against the wall.
Fungal leaf spots would be most prevalent following rainy weather with humid days and cooler nights, especially if the vines do not have good air circulation and the leaves remain wet overnight.
Powdery mildew and leaf spot are usually only a problem when the infections are severe.
Sanitation is key to controlling diseases. Damaged leaves should be removed and all the fallen leaves should be picked up and trashed as fungal spores will persist. Trim the vines and make sure there is good air circulation around the vines. Antifungal sprays can be used but it is best to identify the specific type of infection you have to make sure you have the right control.