I would say it is the type of ballast rather than a bad ballast. Each ballast runs two lamps, two inside are on one ballast and the two outside are the other.
What I would do is replace both ballasts with one new 4 lamp electronic ballast and 4 new T-8 lamps. This is more energy efficient and the lamps will start faster. If you go this route watch the wiring diagram on the new ballast carefully as they do wire slightly different.
If you need more help please ask here.