Should I bleed the radiators?

My radiators downstairs are not heating at all, the one next to the airing cupboard and the next one are heating. But not the other 2 upstairs or any downstairs. Do my radiators need bleeding? Or is the pump not working properly?
Drayton Tempus 3, boiler downstairs, programmer and tank upstairs.
All was working fine until last friday. We haven't been turning off at night just down low. Hot water is fine.