I think so too...OP do you see these "white spikes" anywhere else in your tank? I have a vermetid infestation that grows on my coral skeletons and under rocks. I go in with my bone cutter to nip the snails at the base.
Ugh. I was about to say I used to have them... but I know better. The large ones have long ago been encrusted with coralline algae. Could that explain this weird growth pattern just above this new acro?