Odd lighting discovery, Any thoughts?

[Jason McK]

I run 3X 400W MH 10K XM. on Blueline e-Ballasts. All bulbs were changed at the same time roughly 4 months ago
through troubleshooting an unrelated issue I swapped the middle bulb with the left hand side bulb.
the bulb now on the left hand side was 1000X bluer than the other 2 bulbs. So the next step was to switch the ballast. So I swapped the middle ballast with the far left. So the far left bulb and ballast where back to the original configuration as before I started but they are still way bluer.

Now before I started switching positions I didn't notice any colour temp difference between bulbs.

Any thoughts?

J