typically that lower temp solder is leaded solder.... MOST electronics are now made with 'lead free' solder..which has the higher melting point.. IF the PCBA is made with lead free it is not a good plan to just add leaded solder to it.... different temps mean different reactions and mixing isnt uniform...
The lead free thing started as a EU thing and started big here around 2006 when EU started objecting to leaded boards coming over... they had already switched to lead free of course.

DJ, have you looked to see if the PCBA is labeled 'lead free' or not??