The moment you pick favorites, the rest of the team stops trying for you.

Favouritism does not just upset the people outside the favoured group, it quietly ends the point of trying. If effort and outcome come apart, and the reward tracks who you like rather than who did the work, everyone else recalculates and stops spending energy on something that will not count. They rarely complain about it. They just get harder to reach.

Check who you give the most attention, the best jobs and the benefit of the doubt. If the same names keep appearing, spread the next few deliberately and see what comes back.