The fact is none of us can tell which species of Acropora those might be because none of us have a specimen in front of us. Trying to pin down species based on growth form is a fool's errand. Growth form is mainly a function of water movement: species X grown in one environment can look more like species Y if grown in another. The opposite is also true. This is part of the reason the concept of speciation in coral taxonomy is malleable. The other reason we cannot identify which species these are is that in coral taxonomy, species are not always described as discrete units, as per Veron's discussion of reticulate evolution.