Colts are an exception to the rule most of the time. A colt (depending on which "colt" you have) will grow about anywhere. I'm not sure what you mean by the "youngs coral". There are many different corals that are called leathers as well. Some might do OK under the lighting you have and others probably wouldn't. Although you might be OK with the star polyps, I'd probably wait on the xenia until I had more lighting.