I have a coralife fixture on one of my tanks and I had one bulb burn out a few months back then the second bulb just burned out yesterday. Right now I only have one new bulb in the fixture since that is all I could find locally. Maybe the OP fixture is different then mine but I think most coralife fixtures will work with only one bulb.chances are it's one bulb or the other that's bad. I read somewhere that some fixtures (Coralife I believe) when one bulb goes out the other won't come on , highly unlikely for both to go out at the same time. Or it could be the ballast or starter(if it has one). Probably best to borrow a bulb or 2 and try that first to make sure, they are the problem
Mine is the same as your are too, I wasn't sure if it was a Coralife model , just remembered reading that about one of them being that way. But I agree that it's probably a ballast or something else other than both bulbs going out at the same time.I have a coralife fixture on one of my tanks and I had one bulb burn out a few months back then the second bulb just burned out yesterday. Right now I only have one new bulb in the fixture since that is all I could find locally. Maybe the OP fixture is different then mine but I think most coralife fixtures will work with only one bulb.
I think it is probably that some part of the OP fixture has failed(ballast) rather than both bulbs burning out at the same time.