With the engine cold, but after you notice the leak, feel under the water pump. Mine started leaking like that, with the same kind of drip. Turned out to be the water pump.
Also, if you have a hose in hose set up, if there is an internal leak, you may not see it at the fittings. Check your veggie oil for coolant contamination.
Also, since you have the Aux Water Pump wired to run when the ignition is on, I hope you wired in a 1 amp fuse to protect other items ons the same circuit.
70's SPM #5608 Fairmont A-4 MOW car
06 VW Jetta TDI 145K miles
82 300D 300K My Daily Driver-Warndreicke in the trunk.
Trip ODO still working!
90 Dodge D250 5.9 Cummins/5 speed. 260,000