One problem that's probably not helping is having no nitrates/phosphates honestly. It may also just be that particular coral, they're so finicky. I have several goniopora in my macro tank with nitrates ~20-50 and phosphates usually around 0.2-0.3. One, a green one, had shown some recession but that has stopped lately. The purple one and the red ORA one are always out, and have shown growth, especially the red one. I feed large mysis for my copperband only, no filter feeder food. I have debated lately trying and seeing if they grew faster with that though. I fed a bunch of cyclopeeze tonight, at least my gorgonians liked it
Here they are: