Well it looks like I've lost my two largest SPS colonies.
The blue-tipped Stag has expelled all its zooxanthellae and is completely bleached. The orange Monti-Cap still has some colour left but not much.
Two other smaller colonies are toast as well: (Acropora Lovellei & Sky Blue Loisetteae).
Two large Pocci's don't look very good and my Hammer Coral is hurting, but I think will pull through.
All other corals seem ok. Both cleaner shrimp made an appearance and all the fish are fine.
I have done 3x 20gal water changes, changed the carbon twice and still the skimmer is pulling the blackest, most putrid skimmate I've ever seen. This afternoon I'm going to do a 50% water change and change the carbon again.
All very depressing but I think how much worse it could have been.