Hard Corals are Dyin, Soft corals are thrivin'

[TheReefGeek]

Soft corals like higher nutrients, and will grow faster with nutrients in the water, which is what hard corals do not want/like. If you have a reefer buddy, try their test kits out on your water to make sure it is not water quality.

Lighting could definately be it as well, if you are not running metal halide that would be a good explanation.