I recently had to bury my daughters cat and we planted a lilac on top of him like we did with my cat years ago. Except I planted a Magnolia over mine. I've noticed the bush was doing well for the last 2 months but now it has leaves that are brown on the edges and curling. Did I pick the wrong kind of plant for this? Is there anything I can do to help the lilac? It couldn't be caused by my dog peeing on it could it? None of my other lilacs have been affected by him.