Replacing an Irrigreen nozzle is easy to do and may be required if it clogs with debris. Locate the poorly performing nozzle and pull up the green cap and neck riser.
With one hand holding the neck riser, unscrew the green cap (about 4-5 full counterclockwise turns) until it easily lifts out.
With the nozzle removed, check the filter below and clean any debris (if needed). Hand tighten your new nozzle until it is snug.
Keep in mind that sometimes the issue is simply a clogged filter and not nozzle. Follow this video as needed: