Hey Rocky,
It's actually not coraline. You're looking at the digestive components of the shroom. They can push them out of themselves like that at times and not just out of the mouth. Those components are white in color and are simply reflecting the blue/purple from your lights. As such from a casual glance it does look like purple coraline...
Shrooms will do this when stressed typically or something has agitated them. It happens to some of mine from time to time and it will just go away on its own in my experience. If it continues you may want to consider dipping or various other treatments. Let me know if it is still a problem and I can help guide yah.