new hammer coral affecting gsp?

[e D]

I added a new hammer coral to my 5.5 gallon tank today and i left it alone for several hours. When i looked back at the tank, the hammer is nice and thriving but the gsp is mostly closed up and the green looks sort of shriveled. Could it be that there is some type of chemical warefare going on between them. Any suggestions? Activated carbon in the filter? Thanks.