Typically when I submit orchestrations, the percussionists want everything as a percussion score – so I write all of the percussion instruments as a single player. Maybe this is a bit short-sighted of me, because now they want me to give them individual parts for each instrument.
Move instruments to separate players. You can still create a “percussion score” by creating a new layout, and assigning all players holding a percussion instrument to that layout, in addition to single-player parts.
E.g. using the very simple procedure demonstrated in this video: