What's going on with monti cap?

I had this large piece of monti cap given to me along with another small piece I have placed elsewhere. I know when you see white edges on these that it means they're growing. This one has developed dark edges all around the back of it. Is this good or bad? Also, I noticed a while back a small cluster in the left center of it that just looks out of place. My cell camera sucks but that's the best shot I can get of it and it's towards the back of the tank.

I would say nothing is wrong at this point without stats. It looks like it is slow/no growth right now, check to make sure alk and cal are in spec. Lower light is fine, not sure of placement.