Is it normal for fuel injectors to go bad, one after another in about 3 weeks? on 1999 Infiniti I30

Took the car to mechanic about 3 weeks with knock sensor and injector error codes. He replace #2 injector (stuck open). About a week or so later, same error codes and bad miss reappeared. Mechanic replaced #1 injector. A week later got car back and within less than 10 miles it all started again. What is causing these injectors to go bad one after another???

Asked by for the 1999 Infiniti I30
Best to replace them all at the same time!! Same age and mileage on all of the old ones. Usually cheaper also.
1 more answer
poss bad fuel or old age.