Looks like the mat is covered in algae. You can either take out the mat and scrub the algae off and see if some polyps return. That small bit will not hurt a tank.
First off, WELCOME TO R2R!
I wouldn't worry about that frag crashing the tank. It doesn't look good, but GSP is pretty resilient. it could bounce back. Don't be too disappointed if it doesn't. The tank looks pretty young. It may just not be ready for corals yet. How long has it been up and running?