What is this on my coral?

[Jordan berry]

I came home to this... What is it should I try to remove the reddish brown crap

 

[thedasher]

Looks like red slime algae. Or possibly the mucus coming from the coral if it's either dieing or irritated

 

[Jordan berry]

My corals have been irritated but it's compressing. It's folding in more now. It's a film that can be brushed off. Just red slime?

 

[Jordan berry]

At the moment my calcium is 390 my alk is 168 but my ph is 8.3. I'm afraid to dose but my levels are too low.

 

[NanaReefer]

Looks like Cyanobacteria to me.

 

[Wiz]

Looks it.