its a sign that you probobly let your car run dry of gas before you fill up.

dirt and grime from the bottom of your tank distroy fuel injectors. the fuel filter catches most of it, but its what gets by that kills the injectors themself. If you have run out of fuel all together numerous times, thats will do it too.

If i where you, id change all 4. since you changed one already cahnge the remaining 3