This from wet web media.......
RTN (Rapid Tissue Necrosis)
"Though sometimes referred to as if it were a disease, RTN is not a disease. It is only what its name implies, rapid tissue death. This is when, for any variety of reasons, a coral's tissue begins to rapidly die off (usually leaving the entire coral dead within a few days if not a few hours). Once it starts, RTN is nearly impossible to stop, especially when the cause is unknown. Sometimes a sudden and drastic shift in tank parameters (such as temperature, salinity, pH, etc...) can cause RTN.
IMMEDIATELY remove any coral you suspect to be suffering from RTN. Though it's not known what causes RTN, it has been shown to spread to other corals. This could be because it is caused by an infectious agent. Or, it could be that when one coral dies so rapidly, a significant amount of toxic chemicals are released into the water causing other corals to start dying (a kind of chain reaction). "
I guess the Yuma laying against it could cause it.
yuma must have stung it to death, and the blue legs chowed, either that or RTN got me good 
