RC to phone connection

[hiflyer201]

my RC and Mavic Air connect quickly but my 5S iphone stays disconnected except rarely

 

[hiflyer201]

I think I found the answer to my problem. I'm using an Iphone 5s and even though it has linked on in the past it sure doesn't now. Maybe the new firmware update? I was able to link my cheap Acer tablet and while it linked right up instantly the performance during a flight was downright scary. It lagged way behind the action and completely lost the signal quite a few times while really close but hidden behind some cactus here is the Desert. My 5s has never done that with my spark. I'm guessing a new phone might be the best move. Does anyone have any preferences? I'm thinking 6s or 6s plus