Checking for OS updates is important because updates often contain bug fixes and improvements for battery management. An outdated OS can have unresolved issues that cause excessive battery drain. Checking for high resource usage apps is also a valid step, but since the user has not installed any new applications and the usage pattern remains normal, it is less likely to be the immediate cause. Changing the battery should be considered only after ruling out software issues, especially since the device is relatively new. Lastly, disabling Bluetooth and Wi-Fi does not address the root cause of the problem, especially if the usage pattern involving these features hasn't changed.