GearVr fps drops when use skeletalmesh animation

I am developing vr shooting game for gear vr.

For testing , i spawn two enemies once.
when two enemies both come to player and play attack animation on front of player, the fps drops apparently when playing game on gearvr.
The mobile device is s6.Each enemy has 50 bones.

I have disabled all particle effects and post process, and the scene is quite simple as below.

I have searched for content about skeletalmesh aniamtion on gear vr but found little material about this.

Only finding description about bones limit at this:
https://docs.unrealengine.com/latest/INT/Platforms/GearVR/BestPractices/index.html

How to solve this problem?