Frags discs concern

[goody]

I purchased some of these frag discs awhile back because of their larger size. I believe they are fired ceramic.
Do I need to be concerned about this discoloration after being in the tank or is this normal? Almost looks like rust.

 

[MysticBlue]

I purchased some of these frag discs awhile back because of their larger size. I believe they are fired ceramic.
Do I need to be concerned about this discoloration after being in the tank or is this normal? Almost looks like rust.

They are fine it looks like an algae of some sort. To be honest lots of things will grow on them but nothing to be concerned with.