So I just took delivery of this light which is rated at 5600K. Slapped on the ND64 and took a reading straight off the light. EX1 says 8400K. Took a reading off my white balance card (Digital Grey Kard), EX1 says 11000K! The funny thing is, the card is redder at 8400K. Slapped on the 1/4 CTO that came with the light, EX1 says 5500K.
Anybody here have this combination of camera/light with a similar experience?

I have a couple different LED lights.

They actually vary quite a bit in temp. Current flow through LEDs change the brightness. They use constant current devices to control brightness. They are very different from HMI fluorescent and tungsten lights, and there are a lot of different kinds.

I have been looking into them for a while now. I am building "ring-lights" that will be affordable using dimmable LED's.

I think LEDs are great, but we are only now starting to get a good idea of what they can do. They are not necessarily full spectrum.

It is also possible that your EX1 may give false numbers. The main thing is how does it look on a good monitor and or scopes.

here is the most crasy continual running thread about spectrum analisis of LEDs, and diodes and even incan and such.
Spectrographic analyses, pg. 3 - CandlePowerForums (http://www.candlepowerforums.com/vb/showthread.php?t=200385)
to start at the start of it, you have to go back 3 whole threads besides
Spectrographic charts - CandlePowerForums (http://www.candlepowerforums.com/vb/showthread.php?t=110795)