pretty clean tank...
I can see what you mean about no coraline which is odd as you set up the tank 4 months ago.
I was going to say that maybe the Mg was low but your elos test kits shows otherwise.
I was doing some reading on Mg and found out that it plays a huge part with stabilizing alk and Ca, also it is the 3rd most abundant ion in salt water and apparently the coraline algae has high magnesium content.
If you are intrested read this article:
http://www.advancedaquarist.com/issues/oct2003/chem.htm
I use to have nice coraline algae under the rocks with my MH and when I switched to t5 it all turned to algae, at first I thought the new light was to blame but now think otherwise with lots of calcium in my tank aswell I couldn't understand why the coraline was not so plentiful after reading the article on Mg I understand alittle more....
Btw what lights are you running and what salt are you using?