I’ve not noticed any issues with the putty. When I’ve had a coral grow unimpeded, they grow right over the putty. One of the reasons I’m wondering if it’s not too much light is because it looks like you’re getting good color.
I will say, through all my problems, the PC Rainbow and Pearlberry both died very quickly. Not a slow death like most of them went thru. I’m wondering if the Rainbow is a temperamental coral.