Its hard to tell on a panther grouper which are so white to begin with but I do see some spots. The water appears hazy and can be due to eel's lack of housekeeping as they are messy housekeepers and often drive up Nitrate levels.
If flukes including signs you mentioned, you will see rapid breathing, fish acting lethargic or swimming near the water surface, hiding in the corner of tank or behind rocks, loss of appetite, shaking its head, flashing/darting, develop clamped fins, , or scratching against objects. They may also exhibit what looks like yawning from gill irritation develop, cloudy eyes and loss of color.
Many seem to show on this fish. Assure water quality is good and that ammonia-nitrate-ph are not elevated and salinity is not too low