
A plea for advice: Lilac tree leaves are curling oddly
This potentially sick lilac tree is outdoors in full sun. Watered deeply once a week, or twice a week depending on temperature, about 5-10 gallons by hand shower. Tree is mulched except near the bark. Clay soil but plenty of earthworms and organic matter. Planted 2 years. About 8ft tall.
Has not flowered yet in its life, though the new growth at the very top has some buds set upon it. The leaves are curling in a peculiar way and are bumpy, see attached photo.
The garden has other lilacs that are thriving.
Please help diagnose, would be grateful for any advice!