Your rocks need a bit less detail, they had too much noise/the shading looked a bit dirty.
I edited it (hope you don't mind) to try to give you and example on how they could look a bit better. This edit was not meant to be used by you whatsoever, nor was it meant to say "HAHA IM better than you" etc etc.
I just hope this helps :X.
If you need a better explanation Ill come up with one :p
Yours is really good two, it just needs to be more clear.
Mines the first one