Well, at the risk of being a party pooper, that may not be what's going on here. I think I see two mouths already in the first picture (angle makes it hard to tell for sure). In the later pictures, the peripheral tissue now extends centrally from the upper right so that it overlaps the zone between the two mouths, but I don't think the coral has actually grown. Also I see what looks like an exposed or nearly exposed skeletal plate at the upper right which is where I would guess the tissue retraction starts from. If it's reproduction that's awesome I've never seen it before, but I'd be concerned that there's been some damage there and the coral has reacted to it. The tissue overlying those plates is really easily injured in these meat corals, even by too much direct flow.