What device are you testing this on? It doesn't look like it should be causing ANY problem for fps, at least as far as I can tell from the events you've shown.
What size are the sprites you're using? Is this all lo-fi graphics or more HD style?
(Without the Enemy Spawning Yet)
Ipad 2 = 30-50 fps
Nexus 5 = 50-60 fps
Iphone 4 = 5 fps
Iphone 5 = 50-60 fps
Iphone 5s = 60 fps
Iphone 6s = 60 fps
Samsung Galaxy Note 3 = 50-60 fps
(When the enemy spawn)
Ipad 2 = 20-40 (~20 when the enemy being spawn, after all of the spawning is done, the fps become 30-40)
Nexus 5 = 50-60 fps (~30 when the enemy being spawn, after all of the spawning is done, the fps become 40-50)
Iphone 4 = 5 fps (Cannot even move)
Iphone 5 = 40-60 fps (~40 ish when enemy are spawning, and 50-60 after spawning is done)
Iphone 5s = 60 fps (~45-50 ish when spawning)
Iphone 6s = 60 fps (~45-50 ish when spawning)
Samsung Galaxy Note 3 = 50-60 fps (~30-45 when spawning)
The problem is the lag when spawning for a few seconds
Not placing all used objects in the layout
If objects are not placed in a layout but are created by events, Construct 2 will load the textures for those objects the moment you create them. This can cause a momentary pause or "jank" and make the game feel less responsive. This can be avoided by placing any used objects in the layout. They can be placed off-screen and destroyed on startup to avoid interfering with the gameplay. Then Construct 2 will preload all their textures when the layout starts, avoiding any "jank" as they are created and destroyed at runtime.