No personal experience with this, but great question. Monarch nozzles are generally better than bosch (india, brazil, china).
I'd get another monarch to replace the one. Could just be something got (or still is) in the fuel system and would have damaged any nozzle.
example (from web search):
Blown Injector Tip
It is possible for an injector to blow a tip. This is most frequently caused by air or water contaminating the fuel and affecting the pressure buildup. Some injectors are more sensitive to contamination than others, namely the common rail injectors, so it's important to not only diagnose the blown tip, but the contamination cause as well. Otherwise, you'll continue to have issues with your injectors, even after you replace them.