A lot of the acros we keep are exposed to air at low tide in the wild. Even 2 hours exposed should not have been a problem.
It's possible that there was a sudden swing in temperature (is your tank 80 but your air temp 70?) or light as others suggested that stressed them.
It's possible that there was a sudden swing in temperature (is your tank 80 but your air temp 70?) or light as others suggested that stressed them.