The pop hunk struggled to sing while on stage at the Murrayfield Stadium in Edinburgh, and told the crowd he was battling ill health. He also thanked his bandmates and fans for filling in for him on vocals when his voice failed him, adding: "I'm feeling poorly and finding it hard to talk."Zayn Malik insisted all the pop stars were feeling under the weather, telling the audience: "We've all got colds and are a bit tired. You'll need to sing along because our voices and brains, it seems, are a bit scrambled."Liam Payne added: "Thank you to everyone for being the fifth member because we are a man down."Styles later took to Twitter after the show to reiterate his thanks, writing: "Edinburgh thank you for your help tonight... You're the best. Thank you for having us and hopefully we'll see you again soon. Huge love."