Up until 2 weeks ago my spot lights were working fine, switched on 1 day and they popped checked voltage at light point and it was 70v. Disconnected switch line at switch checked voltage on feed and it was OK at 235v .Whilst still disconnected from switch I send a live feed up switch line and got 235v at lighting point OK. Disconnected lights, reconnected switch line to switch checked voltage at lighting point and it dropped to 209v ,reconnected lights 1 by 1 (with a 12v transformer) and there was a voltage drop each time( there is 3 way switching for lights) can someone advise me ?