I did not notice that my WassUP was not gathering data for a little while, which has been a bit of a pain to be honest. The fix is simple.
- Locate and edit your wp-config.php (I did it in Transmit FTP Client)
- add this line to it:
define( 'WP_MEMORY_LIMIT', '96M' );
- save/upload this edited document back in place
- disable and re-enable the WassUP plug.