Your frustration level must be sky high
This grabbed my attention from your mention of extra corraline growth. I've been having an algae and coral dying problem for quite a while, but corraline has been showing up more.
I have tried everything in my arsenal and it hardly seems to make a difference
I have convinced myself that it is due to the 10+ year old rock in my system. I think the rock and coral skeletons have simply become saturated and are now releasing whatever it is back into the water column.
I'm getting close to taking pieces of rock and placing them in a container of fresh water for a few months, getting the stuff to leach out and starting over again with base rock. I have a number of corals that overgrown the rocks, so it won't be pretty.
Mitch