When we moved in four years ago, we inherited 3 mature lilacs which bloomed profusely until last year. Some of the leaves puckered and then blackened and we got many fewer blooms. Spring had been late and unusually wet--even for the Northwest. I cut every diseased branch back well below what looked diseased. This year, everything was looking fine and then it happened again--as did the late, wet spring.

What is wrong with them and what can I do about it?

Pictures are below. Thank you for any help you can offer!