Why is all my coralline slowing down/vanishing?

[loweryphil]

Calcium 420
Phos 0.25
Amonia 0
Nitrate 0

It was growing like crazy and all of a sudden its started to fade and grow less.

 

[wattson]

PO4 levels being too high and Mag being low..test your levels is good place to start...age of tank too...just some food for thought

 

[loweryphil]

3 months old. I am working on the phosphate with agent green. I am due a water change tomorrow so ill do a larger one than usual

 

[pirate2876]

Check your mag lvls