Pheasants are high energy birds, and unless they have enough space and hiding places can start feather pecking/plucking. More space, Pin Less Peepers separation can generally break this bad habit. Are you feeding a gamebird ration with good protein level?
3 males and 2 females is not a good ratio. If you keep them together, your likely going to find a dead male or maybe 2 or at the least, all 3 males badly injured.
It is also too much pressure on the hens, especially if they have no way to get away from the males.
Choose 1 male you want and put him with the 2 hens. The 2 other males can be separated in another pen, make sure they can't hear or see the hens or they could possibly start fighting each other too!