The spectrum difference indicates that the cold bulb has been changed out for an LED model. The others most likely will be changed out as well as they fail.
A simple web search finds a bunch of screw-in bulbs using LED sources in 1800K, which is similar to an incandescent bulb on a dimmer at a low setting, or a candle. A typical incandescent at full brightness is 2700K. Daytime sunlight is 5000-5700K.
I doubt they're sodium bulbs either, these are really modern fixtures and i see no reason for them to use anything other than LEDs, quite possibly not even in the form of standard bulbs.