My 4-foot bathroom florescent light is flickering, so I bought new LED tubes. But I found out that I don't know how to open the thing. There doesn't seem to be anything to press, the cover doesn't twist or anything, and the ends don't pull off. There doesn't seem to be tabs anywhere either. Not sure where to start looking or what to push. Any ideas? below is a picture of the end of the fixture, sorry for the quality, but the light is flickering pretty badly.