My Miss Kim Lilac is about 15 years old. Late last spring the leaves started turning brown and the I thought I was going to lose the shrub. I quickly dead headed all the spent flowers and pruned the lilac opening it up in the middle a little to get more light inside after noticing the lack of new leaf growth. It has just finished blooming (completely covered in aromatic flowers!) but the only leaves appear to be near the bottom and very few are on the rest of the branches. I've never seen anything like this. If I dead head the flowers the shrub will look like it's dead. Please advise. Diane Pearson