Firstly, you need to get your nitrates down, they are way to high. A 2 & 1/2" sand bed will do nothing to help nitrates, it's to shallow to benefit. If you want to run a DSB, you need a minimum of 4" IMO to benefit from it.
I would also try to raise your calcium to around 450ppm, magnesium to 1350ppm and salinity to around 1.025-1.026. These levels are much closer to NSW.
Also with your dosing are you testing for stronium and iodine? I wouldn't add anything you can't test for.
Feeding may help turn the Hydnophora around, phyto and finely minced marine products. I would recommend it, and see how things go.
As for your Tubipora (pipe organ) well this is a harder species to keep. Tubipora need strong flow to prevent detritus and algae from settling among the tubes. Another one that benefits from phyto and zooplanktons.
I have a tubipora, that only had a few polyps when I bought it and it was an impulse buy. It has not grown any more polyp in the year I have had it, but I found that with increased flow the polyps have expanded more regularly. These are not an easy coral to care for.
HTH