Looks like the flow isn't too much (hard to say from a pic, but the extended tentacles seem to be able to stretch where they want). If lights haven't changed it is highly unlikely that is it.
Temp, pH, salintiy and alk are what I would look at. Specifically for swings in parameters or for extremes. Temp and pH have a tendency to get ignored in the hobby and can have significant effects if they start to go out of control. High alk will also do significant damage to LPS. If you do have a pH issue I wouldn't immediately start buffering but instead figure out what might be causing it (low alk, low mag, high CO2, might need hydroxide to balance carbonate/ bicarbonate ratio). In a 40 breeder water parameters can swing quickly as your water volume is likely only 20 gallons.