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Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/vines/wisteria/grow-wisteria-seeds.htm

I would look at the root system. It may have a root rot brought on by the rain. You don't need to dig the whole plant up, just dig down to the roots to examine some of them. If they are mushy and smell off, it is a root rot.

Some root rots can be corrected and some cannot. The best you can do is to make sure drainage is good and treat the soil with a fungicide. If the root rot can be treated, this will help. If it can't be treated, nothing will help.

It actually sounds like it may be a fungus, but there are several it could be. I would treat the plant with a fungicide. Just in case, check the roots for root rot, as this may also be possible.

Wisteria are pretty hardy and tough to kill. It may be having a tough year this year, but it will likely come back full strength next year.

I would suspect that the culprit is thrips. Some thrips like to attack the flowers and young growth on a plant and the tips would be young growth.

This article should help:
https://www.gardeningknowhow.com/plant-problems/pests/insects/controlling-thrips.htm

Yes, this vine will eventually kill the trees they grow on. If this is becoming an issue for you, then pruuning the vine back may be necessary OR you may need to consider getting rid of it altogether. These articles will help:
https://www.gardeningknowhow.com/ornamental/vines/wisteria/pruning-wisteria.htm
https://www.gardeningknowhow.com/ornamental/vines/wisteria/controlling-or-getting-rid-of-wisteria.htm

It is likely a fungus causing that. Treat the plant with a fungicide (like neem oil) and that should fix it.

I would also check for crown or root galls. Here is some information on them that may be helpful: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6710