At like the 6-7 month period I got some.
I tried to treat it but the only thing that really worked was a total black out for 2-3 days. I covered it with a sheet and turned the lights out and prayed. All my coral did fine. LPS, SPS, and softies.
I used the chemical agents after this for a couple of times and they kicked what was left over.
The red slime came from adding some LR but I did cure it for 3 weeks so I think it happened from a slow release of nutrients. Which is the only reason I can think of why my many water changes didn't help.
To start with sypon and blow off as much as you can, reduce lighing by a few hours, and do a couple of 25% water changes a couple of days apart.
Good luck