How old is the battery? You can have it checked at most auto parts stores. They only last a few years even the bettter grade ones a little longer.
I think there is a 20 amp fuse located near the battery that you should check.
Last, if you washed it the connectors on the engine are in a position to catch and hold water, they may have shorted out the rectifier/voltage regulator.
There must be a wire pinched somewhere shorting out the system. You do not have an electric pto so the only wires go to the headlights. Check near the front of the frame by the hood hinge that is a place where they could pinch easily.
Did this new symptom start after cleaning the connectors?
I sent you a PM for more info.