Although it's pretty easy to find fault in Bottas, you can't really blame him if the CC slips away from Mercedes. As the #2 driver, all you can expect/ask from him is to beat the #2 of the opposition. Bottas is ahead of Perez by 13 points right now, so he's doing his job. Hamilton as the #1 needs to beat the opposition's #1. Right now he's trailing by 8 pts. So if Mercedes loses the CC, it might be more fitting to blame it on Hamilton.
Of course this could all change in the next two races, but as it stands, it's Hamilton that needs to do more.