The origin of the subscriber plague is unknown, but it is possible that Katie's roasts indirectly affected some subscribers causing them to kill themselves.
The Plague Edit
Liam once held the god like subscriber count of 260 subscribers, it can be shown that he originally had more than 200 subscribers as he had made an 200 subscriber special. However, an unknown plague caused a large amount of subscribers to drop off, leaving Liam with 190 subscribers. Many surviving fans suspected that it was the work of Katie, but Liam being the proud noble man he is, denied those claims.
The Aftermath Edit
No one knows what happened to the subscribers, no one believes that they will be seen again. However Liam just simply believes it was a glitch, telling us that we should not fear the plague. Showing us that he his truly looking after, Our Lives.