Osram Tree acting odd

[HIDLamp]

At my part time work in a cafe there are 8x 6' single SS fittings. All of them have Osram Trees fitted and appear to have been installed at the same time as part of a bulk change. They are 5 years old at least and do about 7 hours 7 days a week from Easter to The end of Oct then weekend till the end of Nov. Anyway today I walked in and noticed one was noticably dimmer and slightly green compared to the others then after a about half an hour it brightened up to match the rest before dimming back down and brightening up and dimming down very gradually over a few hours. Is this the tube going EOL, the ballast going EOL or what. This light is on the same switch as 3 others and I suspect the smae phase and breaker as the rest of the lighing in the room so not voltage. Any ideas?

[Danny]

An unusual one. I would guess it may well be going contaminated. Reviving its self then going back contaminated maybe?

Either that, or was it cold in there could the lamp be dimming down triggering the starter?

[HIDLamp]

It was a bit chilly but not excessively cold. I'd have expected the one by the door to have been doing it not the one over the coffee machines. I do like the contamination idea though. It sounds very plausible. Hopefully it'll manage another 39 hours to see this season out and shouldn't be needed again until February

[Nick217]

Could be as it's over a steam/heat source..

[HIDLamp]

Never done it before though. It's about 16-18ft up too.

[Flurofan96]

Contamination due to impurities maybe but partial vacuum loss, also a candidate however that would exhibit a dim hot pink glow

Having got recently these OSRAM Lumilux 58W tubes with the green tree logo in cold weather in my shed they started up with a large pink purple glow but that went away after 8 mins of runtime