Can anyone tell me what is going on with the dodgy leaf near the crown of my phalaenopsis?

For years, it did well, on a shelf in front of a north-facing window here in the southern hemisphere (Sydney). I watered it once a week and kept it properly drained. Now, suddenly this leaf looks terrible and one of its emerging flower spikes has died. Should I take it out of its pot and check the roots? please see attached pic.