hello. we have some lilac bushes that are several years old, maybe 10-12 years. they do not bloom very well, and never have the nice scent a lilac is supposed to have. my wife tells me we need to amend the soil with something, but we dont know what. this is clay soil in west-central ohio, but we did add compost and organic fertilizer when we planted them, years ago. i have a couple of pictures to post, if i can figure out how to do it, lol. any help would be greatly appreciated. thank you!