Would be great if you can show a little bit of info (about the last matches lost, your quality adn quality of opo', and the stats of your team) but this should be in another thread cause we are going out topic here
But basically you should think that the players have, despite the visual quality, their internal quality, which is different. So, more than a change of formation or so I think you will need to check well the players that are doing a good contribution and those who are not, and prescind of some of them.^^