I would suspect water issues to be honest. trachs dont bleach out and die that quick without either too much light or poor water quality. Post your Calc, Alk, Mag, Sg levels this way you wont have this issue again.
i had a favia tip over and lay face down for a day and when i flipped it over it looked fine but then completely bleached and lost all of its tissue the next day. Alk could also be the culprit