Posted the reply early.Yes, that appears to be an algae or residue of some algae you may have killed or annoyed from the dip. What did you dip the coral in?
Nonetheless, GSP is very hardy and normally does a good job of fighting off algae. I suggest assisting by blowing it off with a turkey baster daily or every couple of days and making sure you don’t have any water parameter issues that may contribute to algae growth, such as high phosphates.
Also, your tank is very young and algae blooms should be expected.