Metal Halide Lighting Problem

72chevy4x4

I just replaced 8 (all) metal halide 175's in a gymnasium-all was well for the first week, now two of them only glow blue upon energizing the switch. Is that indicative of a ballast problem? Observed behavior was greater than 5 minutes-the remaining 6 lights lit with no problem during the same time frame. No flickering of lamp (overheat indicator).

Magnettica

Have u tried using one of the good lamps in the fixture that's not working correctly?

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