mobile game FPS drops on objects first load

Hi i’ve made a small level with 1 barrack, 1 house, 1 tower and 1 larger building. I copied some of them in UE4 to avoid adding more new objects. The objects are all from 400-3500 triangles with UVs from Maya. I imported with help from:

I also set auto LODs on every object to 3 and filled the houses inside(they were previously with holes in the walls and you could see through the windows).

The problem is when I start the game on mobile(iphone 5s) for the first time, the game FPS drops and goes back to normal whenever I get near a new object on the scene. If I add a cutscene with rotating camera around the scene, I get more fps drops due to the quicker object loading. As you can see in the image example the scene has very few low poly models. The only high poly is the default character from the engine. Also this only happens on mobile. I even tested the game on iPhone SE(better hardware). On PC I cannot notice anything probably because of the better hardware.

Is there a way to load all the objects at once or some other fix that?