Hi krisolson,
Your
Xenia and
Corallimorpharia 'shrooms are probably still in shock over the water changes, not to mention the initial nutrient spike from the dying
Gonio
Even if you balance pH, temp and Alk with the old water, there is a substantial 'thinning out' of organics in the water that those softies can 'taste'. On top of that, many quick-dissolve salts contain harsh buffers whose relics take time to fall out of solution or escape to the atmosphere.
Time, good lighting, an end to frequent water changes, and patience may see them returning to their former, expansive comforts.
hth,
horge
PS:
Goniopora are very notorious for dying on hobbyists: their ability to process ingested food is seemingly tied to their ability to utilize the sugars made by their hosted zooxanthellae.
In other words,
If they aren't lighted properly, they may not be able to process ingested food.
If they aren't eating they may be unable to take advantage of available light.
