iOS FPS low frame rate when character moves, profiler shows Physics.Simulate takes cpu time

We develop FPS game for iOS. Player character is a First Person Controls from Standard Assets (Mobile). It has standard Character Controller attached.

We have 7 enemies on our scene Each enemy has a non-kinematic RigidBody. Enemies moving to the player when player is near

Scene has 5500 triangles / 6000 verts We have 20-25 fps on iPhone 4 when player don't move. When player start moving, fps falls to 7-10.

Also, we move enemies by changing their transform directly, not by calling AddForce.

In profiler we can see that Physics.Simulate takes about 60%-70% of cpu when the player moves.

How should we fix this?

We are new to Unity and 3D. Sorry for my English.