It'd be a bit morbid to remember Amy Winehouse through "Rehab" even if Coldplay's version, which they performed at the Splendour in the Grass festival to lead into "Fix You," wasn't so somber. The thought's appreciated, and covering Winehouse live is far from exploitative like some "tributes" can seem. And there's a rationale. From Coldplay's website:
Later, Fix You brought us from the celebration of birth to the acknowledgement of a tragic death. There’s little that can be said about Amy Winehouse’s passing that hasn’t already been said. It’s just such a sad waste. We’ll leave aside the awful irony and just let the Aussie choir sing.