Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.

 

In the Name of Allah, Most Gracious, Most Merciful.

 

All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.

 

Janazah Prayer essentially consists of Du’a for the deceased. So, there is no need for another Du’a after the Prayer.

 

Of course, we should offer another Du’a after the burial.

 

Having said this, if someone offered a supplication in the language of the people for those who do not know Arabic, you cannot condemn them for doing so.

 

Allah Almighty knows best.