Device battery draining and overheating when MCPE is in background

When MCPE is closed and still is in background, device starts to overheat and the battery drains much faster.

Affects Device(s):

iPod Touch 6th Generation - Full brightness
iPhone 5S - 25% brightness

These devices seem to overheat and battery drains faster when Minecraft is in background. Doesn't seem to affect the LG K7 - Android 5.1.1