Number one........your rajah is growing faster than mine. Mine is soooooo slow!!!
Lets get back to the topic. Well, I don't know what it could be or how it ended there, but for me, all my LFS is becoming a little greener. Something like yours. Maybe it could be reviving like what Athene said, maybe it could be moss, but one thing I know for sure, it won't be damaging.
Unless it spreads out and covers the whole pot..............muahahahahahaha.....
Cheers