perhaps too much flow combined with plenty of light???
The flow is described like that which we normally use for a four to six ft (i.e., larger) tank. Here, its in basically just 2 ft across and the rock arrangement may be adding to that so the flow is in fact pounding on all the corals.
You might consider turning 3 of the 4 off for a few weeks and see if things start taking a more normal growth form.