When a manufacturing company first starts up a run of lamps the first ones off the line will be a higher kelvin and when they quit there run the last ones will be a lesser kelvin. Your 400 might of come off of the beginning of a run and your 250's the end of a run. Or they might of sent you a 20K, it's not the first time someone has put the wrong bulb in the wrong package or marked it wrong, take it back.