Yeah my comment was thinking about not enough light being on the sand.That's a nice colony, mine was on the rocks for a while but put it on the sand a couple years ago. It's doing well on the sand also. As long as it's not buried should be okay.
I just think the op's is not getting the light it needs. For that, I say move it up some.
Also the OP has cyano rn so prob not great for it to be on the sand from that perspective as well.