Should the ballast be replaced?
First I check for obvious fitment of the tubes and conditions of the tombstones.  For instance one easy problem is failing to rotate the tube a full 90 degrees, so it doesn't properly engage.  On T8/T12 tubes there are score marks to help tell you where center is.  Can't speak to T5.  

If that all checks out, and fitting new lamps doesn't make them all light, or if the ballast has a rep for burning up lights quickly, or is leaking goop, smelly or buzzing loudly, then I condemn it by snipping all its wires flush at the ballast.  That assures no one wastes time trying to reuse it.  

Otherwise if it is a magnetic ballast, I cut or unhook its wires in a non-destructive way, and stick it on the shelf as a usable T12 ballast (I only fit new T8 ballasts).  That happens when I upgrade a 2-ballast fixture.

Then I slap in whichever electronic ballast I please to, with a strong preference for rapid start or programmed start ballasts.  If a fixture had a serious arcing problem, I would shun the arcey instant-start ballasts, and favor programmed-start ballasts as they have a startup sequence.