Vauxhall Astra washer jets

Not sure what's fitted on yours , but common fault is gunk / soap clogging up pump filter .Removing and cleaning out usually fixes .

There is only one pump for the washer, it rotates in different directions depending on whether it is for the front or rear screen. As already suggested the pump can "gunk up" and only manage to rotate in one direction, try filling with hot water (as hot as possible) and flushing through, this cleared mine.