Cardboard performance issue on QHD LG G4

Hi,
I’ve got a problem with my VR app in terms of frame rate when packing it on Cardboard. The app is made of cube with 6 2048x2048 textures and few points to change location of viewer, so it’s nothing fancy and laggy.
On my LG G4 which is QHD (2560 x 1440) resolution the framerate is around 35 fps and it’s very uncomfortable when rotating head. I’ve even tried to hide everything, so the view was pure black and empty, nothing to render and still the framerate was around 45 fps.
On Xiaomi MI5 which is FHD (1920 x 1080) resolution the framerate is smooth and still 60 fps.
I was thinking that maybe LG G4 isn’t capable of rendering QHD VR smoothly. But it doesn’t seem right to be unable to take advantage of its QHD resolution since it isn’t very old and bad phone.

So my question is to those of you who have QHD phones. How many fps do you get on your VR cardboard apps or do you know on how many an average QHD phone should get?