I'm have 3 lilacs in a row, last year and especially this year, the oldest lilac is really struggling with leaves. It's only older than the other 2 by 1 and 3 years but you can see the difference in the photos. Its about 7 years old and planted in full sun. It was sitting next to a broken gutter for about 3 years, maybe there's a connection? Blooms are fine but all the leaves are almost gone. I tried to remove 2 large limbs last year which did nothing, and 1 this year, with very little regrowth. Should I give it hard pruning? I really need this shrub for privacy.