I just recently had a hammer starting to go down hill on me, when I had it in the temp tank. The hammer started bleaching and exposing some of its skeleton when the water conditions went down hill. All the other corals showed signs of bad health as well. However once I got them back in the main tank (it’s only been just over a week now) everything started doing much better. The hammer is sill bleached, but it is all ready starting to come back. I can now see some color is some places plus it is expanding much more than it did before, but not nearly as much as it did in the past. Just try to keep it in a moderate flow and keep good/stable water conditions; do a water change if you have to.