How about magnesium? I think IO salt is generally a little low so you likely are as well. Several years back when I started running GFO and boosted Mg to fight hair algae the coraline algae growth really took off in my tank and the general stoney coral growth increased as well.
Aquarium Chemistry: Magnesium In Reef Aquaria
By Randy Holmes-Farley, Ph.D.
http://www.advancedaquarist.com/2003/10/chemistry