Nah if I think there's an actual fault I'll call the electrician. I'll just give it a few days to run the toothbrushes down, double check if they charge there, then if they don't I'll try another plug.
Ok, if this real and not your imagination (don't kill the messenger) get a sparky to do a fault loop impedance test on the plug in the bathroom. And in the meantime don't go testing it with high power devices like hairdryers
I suspect Bung might have nailed it