Is this coral looking good?
 

I had him on the rocks and he looked like this


After I moved my rock and moved him to the sand bed an now he looks like this

I think the bubble needs more light or more food, feed them when lights off and tentacles are out.

I feed mine chopped up silversides.

So he should look more like the picture on the rock?

Leave him where he is for now and see how responds. I had mine on the rocks when I first got him, been on the sand for months and is fine. What kind of flow do you have in the tank?

I wouldn't worry too much as of yet, it could be deflating simply due to a water change or a change in lighting or tank placement change.

I just moved a green open brain into my new setup and it did the same thing,
simply due to increased lighting(hear that brad lol) and also because of a
temp change.

If you want to feed it some mysis or silver sides, that's best at night when all its feeding tentacles are fully extended.