All shared hosting account shall be allocated with certain memory to the domains. 

When the site/hosting running out of memory, users shall encounter certain issue eg, installing a new theme/plugin or even upload new media to your site. 

In the event that you have encountered with the error message that reads below

“Fatal error: allowed memory size has been exhausted”

You may try on increasing the PHP memory limit by editing your wp-config.php file instead. 

To increase the PHP memory limit,  you may logon to your respective control panel to make the changes. 

cPanel - applicable to cPanel hosting server only

Your hosting provider allocates a certain amount of server memory to your site. In the event that you reach your server’s memory limit, you may run into issues installing a new plugin or theme, or uploading media files to your site.

Instead of successfully adding your new resource, you’ll see a message that reads: “fatal error: allowed memory size has been exhausted”. If this happens, you can try increasing your PHP memory limit by editing your wp-config.php file.

Alternatively, you could check how much disk space you’re using, see if you can improve your PHP memory limit, and consider upgrading to a new hosting plan that offers more space for your growing WordPress site.