Hi i have 6 robus bathroom lights that run off a 12 v transformer. The problem is that after around 10 mins they start to dim and and then hardly any light is ammited. a live swith wire comes from a jb goes to a pull switch, then the transformer input is wired to the neutral and switched live at the jb, then the lights are looped to the output on the transformer. these have recently been installed, could this be a transormer problem? i have a multi meter so can check the voltage output on the transformer and at each light. thanks..