New Setup, is this a pest?

[Wingin It]

each head is the size of a nickel, maybe a tad smaller than a quarter. Green in the center and brown otherwise. They had congregated on a small rock that you see in the pic, but a couple have shown up on two other rocks. The live rock came from another persons setup that I just bought.

[banditpowdercoat]

looks similar to some large head polyps I have. if you keep them away form other rocks, they wont migrate.