As you will know VnV the FA are very well aware of the human factors relating to their job, as I am sure you are aware of the health risk related to sitting infront of a computer all day, writing software. Does RSI mean anything to you? Of course the FA looked tired. They had been on their feet, looking after about 350 people who didn't seem to know the words "Thankyou" or "Please", or "Excuse Me", only "Give me this", "Get me that", or "I Want".
I am not saying that there isn't a problem with air quality on the B777. I have operated as a FA on the B777 for almost 2 years, and do notice a difference while in flight from the aircraft I have operated in the past (B737, B757, B767, A320, A321, DC10).