Bad cyano

[saltyair]

Here are a few things to look at first.
1 how much flow - you might need to increase the flow or point a power head toward the sand.
2. what is your po4 and no3? - you might have a nutrient issue. Tap water? if so what is your TDS. Doing water changes could be adding to the issue.
3. what type of lighting? what is your photo period? Might have to change bulbs or eliminate the red spectrum.
4. Quick fix and works fantastic redcyano rx - but will come back if other points are not taken care of. It is common for setups that have been up a year or less.
5. cyano loves low PH
6. how much are you feeding?

The plate coral does not look good - IMO i would dip it (brown jelly) and place in a high flow area.