too many cooks spoil the broth

 آشپز که دوتا شد آش یا شور می شود یا بی نمک

 too many people involved in an activity can ruin it

EXAMPLE 1: After Bob and Susan edited Nicole's college applications, they were worse than when she started. Too many cooks spoil the broth.

EXAMPLE 2: You don't need to help us. We have enough people helping already, and too many cooks spoil the broth.