Some of the fancier transformers actually have multiple voltage taps, they have screws for 12, 13 and 14 volts. Thats to overcome voltage drop on long runs. The one I worked on like that they weren't labeled at all on the case either, just 4 screw terminals. So it's possible that they really are running the lights at 14 volts even without there being anything wrong with the transformer. A quick google for a Kichler 900W transformer, the pro model at least does have 3 taps like that.
