So what (fa-mā: the subject) is wrong with them (lahum: the predicate thereof, semantically connected to an omitted clause, the person of which has been transposed onto it) that they turn away (mu‘ridīna is a circumstantial qualifier referring to the [suffixed] pronoun [in lahum, ‘them’]) from the Reminder — in other words, ‘what has happened to them that they have turned away from admonition’ —