You can see what applications are doing in terms of battery consumption by going to settings > Battery > battery usage.
As time goes by using our phones means we do tend to install more and more apps, many of which will use up more and more resources such as power. By looking in the battery settings you can identify heavy users of data. Often 3rd party internet security apps and social media apps are heavy users of battery.
The other thought which you mentioned is that your battery may be faulty. It is true that all rechargable batterys deteriate over time but your battery does have a warranty period of 12 months. If you want this checked for free you can go to your closest Samsung Support Centre where they will conduct the necessary tests for you.
Here is the site you can use to find your closest Support Centre:
Hope this helps.
There are a few things which can affect the battery life of a device, these include:
- running applications in the background
- not using the original Samsung fast charger
If you are a heavy user, on the device there is the power saving mode located in settings then battery. This will increase the battery life of the device.
Hope this has helped.