Looks like they are being irritated by the algae around/on them, at least the lowest ones. Could also be proximity to any nearby corals? Take a small airline tube and gentley siphon off the algae. It should help some. You should also address the algae concern itself and what might be causing it.
Cyanobacteria, AKA Red Slime Algae
Can you post a little tank history, tank mates and water parameters other than what's listed in your profile? How close is the coral to the light source?
Cheers
Steve