Red Macro getting crust on it - tips to fix this?

[Newms118]

So I have this red algae that I believe is a Gracilaria Hayi. Its at the bottom right of the image here:

Notice that it looks kind of white. Its not bleached, but instead it has this gritty something on it. Its a bit brown and I cant tell if its just dirt or some coralline algae. I can scratch it off and the leaves underneath seem fine. Also, the plant feels more crusty/crunchy, not so flexible as when I first got it.

Any idea what this is and what I can do to stop it from forming? Some of my other algae have also shown signs of it growing on them.

 

[Michael Hoaster]

I've seen coralline algae encrust red algae in my tank. Yours sounds like a hitchhiker on a new plant. If you don't want it, scrape it or cut it out of the plant. If you're running a calcium reactor, maybe turn it down.