Split injector tips are often caused by dry starts and there is also a theory about water in the fuel causing this.

Splitting the injector tips are primarily caused by improper fuel system bleeding after servicing the fuel system, including a filter change or other issues where the injectors stop getting fuel. 

 Because “dry starts” cause injector tip failures, a procedure that primes the fuel system before starting the engine must be followed. When the fuel injection system is dry after engine service, cranking the engine to start without first priming the fuel system will result in an overload condition in the injector tips. This overload occurs because there is no fuel present to cushion the needle valve as it lifts and seats.

One method of priming the fuel system after service or running out of fuel is to cycle the key a few times without starting the engine. 

Split Fuel Injector Prevention

• Avoid running out of fuel
• Prime fuel system after service or running out of fuel
• Be sure to drain the water separator regularly 
• Inspect fuel filter for restrictions, replace according to manufactures recommendation
• If the vehicle is to be stored for a period of time, arrange to have it started on occasion to prevent internal varnishing and corrosion of internal components
• Use fuel additives specifically designed for stabilizing diesel fuel