Those little mushroom things look like Palythoas. The dust is probably just an accumulation of detritus. You might want to get a small power head and use this to blow the detritus off the rocks right before a water change.
http://www.advancedaquarist.com/2003/2/inverts
Thanks, I was using turkey baster to blow away gently. Will use small power head to take care of the rest.
So these palys or ok to be there right?