Iphone 6s plus screen has a pink tinge and the top of the screen is flickering

My iPhone 6s plus screen has suddenly got a pink tinge and the top of the screen is flickering. Has anyone else had this? Is there a way of fixing it? I've done a reset and it's still there. I've noticed the phone has been running slow for a few days, but the link tinge and flickering has only started today. Any suggestions would be appreciated. Thanks