Alk now at 10.5 as of last night and cal 440. Still going to let it drop some more before I worry about dosing anything. Could the high alk have been causing this?
Algea seems to always grow on frag racks, might be the material or that it just has lots of pockets to hold nutrients. Is it a new rack or recently put back into the water?
Sounds about right to me. I find it best to wipe it down, get as much as you can out, put a snail right on it and frequently blast it with a turkey baster. Another month and it should go away. You can always remove and scrub with vinegar but if it's leaching stuff it will continue.
Now my racks are covered in coraline, zoas and other coral bits that have attached.