Birds Nest and Frog Spawn dying - stems browning

[MigReefer]

My Frog Spawn and Birds Nest coral stems are browning and slowly dying (see pics).
The stems are not slimy and the color seems baked in the stems as not much comes off when i scratch them.

Do you have any idea what could cause this and how i can fix this?

 

[19Mateo83]

First thing first, please post your current water parameters and a little information about your system; size, lighting, flow, age, etc. A full tank picture will also be helpful.