Hi - The symptom on your peony is a very common problem called peony leaf blotch (Graphiopsis chlorocephala). It is a fungal disease that is exacerbated by moist, humid conditions. There is not any type of remedy for it once symptoms appear. It is not fatal to the plant. Avoid overhead irrigation to minimize leaf wetness. At the end of the growing season, prune off the foliage and discard it in the trash (not compost). https://bygl.osu.edu/node/1182
Lilac: It is fairly common for old lilac foliage to look like this in late summer. Lilac borers, root problems, and powdery mildew (or a combination of these) can result in decline. Lilac benefits from regular pruning and thinning to keep the plants healthy and vigorous. Prune out weaker growth and branches. Dead branches can be pruned out at any time when the weather is dry, but regular pruning is best done immediately after the plants finish flowering in the spring.
The Hibiscus has unusual symptoms. We cannot tell from your photo if the small brown spots on the leaves are raised bumps or if they are dead brown areas where the foliage was scraped. Are you able to push off these spots with your fingertip (possible scale insects)? Do you see anything on the underside of the leaves? Do you recall when these symptoms/spots first started to appear? The curling and puckering of the leaves looks like herbicide injury. Growth-regulator-type herbicides can drift and produce these symptoms. https://extension.umd.edu/hgic/topics/herbicide-damage