Site running really slow – believe client uploaded corrupt image.

Hi there,

A few days ago my client contacted me saying their WordPress site was running really slow, and some image content was no longer appearing in the homepage.. The dashboard is also running super slow on the Media Library ‘view all’ section, when it eventually loads, it comes up with the following error:

“Fatal error: Maximum execution time of 30 seconds exceeded in /home6/liliscut/public_html/testing/wp-includes/functions.php on line 1366”

Here’s a screencap of the error..

I’ve tried to delete all the uploaded images from the FTP folder ‘wp-content > uploads’, but it didn’t fix anything.. Could somebody please help me fix this problem.. My client wants to get the site up and running asap.