iphone 6 plus has become very slow after updating it to ios 10.3.1
exactly after 2years of purchasing iphone 6 plus 64GB, it has become painstakingly slow. It has still 19GB storage available.
iPhone 6 Plus, iOS 10.3.1
Take a look at this article, it may help you http://www.macworld.co.uk/how-to/iphone/how-to-speed-up-an-iphone-3463276/