The leaves of this plant of Lords-and-Ladies (Arum maculatum) were strangely puckered where the dark spots were. Although dark pigmented spots can occur naturally, where they are puckered it can be the result of infection by a fungus Melanustilospora ari but at the time of taking the photograph I didn’t know that and so didn’t take any further photos so am not sure that the fungus has caused the puckering on this leaf. It needs further checking and ideally a microscopic spore identification. To be honest I’ll just look out for it again and take more photos and see what turns up.
Black marks on a Lesser Celandine leaf turned out to be the rust Uromyces ficariae which is more more common and worth looking out for to see if you can spot it.