FPS drop on mobile ( IOS )

The device that I am currently using is the iPhone 6s Plus on iOS 12.3 1 . On 1.11, the fps would drop once while but when I updated to 1.12, the fps got even worse making my device unusable. I have to lower down the render distance to 6 but it didn't improve the fps. The max render distance this device can go is 12.

In the video you'll see the fps drops but it happens every where when I explore and it gets much worse as I play the game longer which I was not able to capture that in the video.