Almost all the other labs properly comply to the modern 6500K colour standard, as far as I'm aware.
Terrific. Even though it seems very unlikely, we can't discount the possibility that the cable is failing, so if you had another HDMI cable around the house that you could try, that would be handy.
You mentioned the calibration of the external screen; do you keep your laptop screen calibrated too?
What did the lab say about the prints?