Can't really answer any questions without levels.
Ca, Alk, Mag, Salinity, Nitrate, Phosphates?
Lighting?
It seems as if your Digitata is doing nice, while it is an easy coral, your other acro is not so "easy."
Issue could be shock. Issue could be, if you're using LED's, is it's blasting it with light it is not used too. Issue could be both, resulting in death.
Explain to us more about your tank so we can help ya!