Dramm uses a Clean-Out Anti-Drip Valve with the JETRain nozzles; a ¼ turn on the slotted cap will open this valve. Remove the silicone diaphragm, clean the backside of the diaphragm and see what debris might be inside the valve. Remove, clean and re-assemble. It’s that simple.
When unassembled if you see a constant trickle of water dripping from valve, you might want to examine your solenoid valve. Open Solenoid valve and examine the diaphragm and seat to see if there is debris build up that needs cleaning.