Thanks for the reply BirdLover. That seemes plausible, the sick one is right on the neighbour's fence. A couple of weeks ago I looked at the bottom and realized that the sprouts on the ground weren't lilac but a fruit bush from the neighbourh's side. The plant looks like raspberry but the berries are one-piece round red. I pulled them all out from my side.
Maybe I'll get lucky and that was the problem and it will recover next year... hopefully they didn't put any weird fertiilizer on - the slope comes down into my yard. For myself I don't want to put any fertilizer on until I know what my soil needs, and I don't yet know how to figure that out
![Smile :)](./images/smilies/icon_smile.gif)