I have 5 droplets created at different times, older one Oct 2016 with Ubuntu 16.04.1 and newer 16.04.2.
All of them have nginx php7-fpm and Grav CMS on it, nothing else, same exact configuration of the files in www in...
if you run:
sudo du -h -d 1 /
On a new vs. old machine that should tell you which of your top-level directories is taking up extra space.
Probably either /home or /var
You can then run:
sudo du -h -d 1 /var