Potential MH problem

[Dez]

It's probably one of your ballasts that is starting to go. I had an ice cap ballast go on me but it still lit the bulb, but it was significantly different to the eye and a bit dimmer. I tried switching my bulbs around like you did and got the same results. I put a new ballast in and that solved my problem. But in your case it's a built in unit, so maybe try the warranty route....kind of sucks I know.