Problem with a 'fault' drive status and a red LED light

My Cloud OS 3 Personal & Network Attached Storage My Cloud EX2
1

I noticed my enclosure had a red LED light on and then checked in the system and noticed there was a fault on of the drives. Do I need to replace it with a new hard drive or can it be repaired?

2

Red light can come on when the drive is 90-95% full.