Sudden Coral Tissue Recession

[Dinkins Aquatic Gardens Verified Sponsor]

What causes sudden tissue recession? One hammer just suddenly lost an entire head, as did a frogspawn. Multiple corals are retracting their polyps as well. Parameters are all good.

Last night the skimmer overflowed a little during sump maintenance, and salinity dropped from 1.024 to 1.023 and then I raised it back up to 1.024.

Any ideas?

 

[JGT]

Something’s up with your H2O.