new coral bleached

[sheeba]

I bought a mushroom 2 days ago, and the skimmer had emptied half the tank onto the lounge floor carpet, (the skimmer is now sitting close to the edge of a window waiting to be pushed!!) so I had to do 50% top up with a new type of salt. (the LRS said this was fine to do and large changes with a new salt was OK, I now know differently) The mushroom developed bleach spots and a few more today.
I don't know the exact name of the coral as the RS couldn't tell me, so an ID would be much apppreciated too.(getting a new camera in a week so this photo lacks somewhat)
What can I do to help the coral?
All parameters are ok.