FPS drop down in some android devices

I am new to unity and this is my first game every which I am developing in 2d.

Everything is working fine except some android devices where FPS drops down below 10. While same is working fine in other android devices and iOS devices with nearly 60 FPS and more.

I have row of gameobjects moving from top to bottom with specified speed.

I have noticed that till there are one or two rows it moves fine but as rows increases frame rate starts dropping down. I am destroying objects once they goes off screen. At most there are 10 to 14 moving game objects on screen. Destroying and generating rows is continuous cycle.

I have visited almost every question targeting "Frame Rate" and tried every solution with no luck. I have been finding a solution from a week and now this is just driving me crazy. There is nothing that I haven't tried. I even have no idea what to ask now.

I am using unity 5.3.0 and for moving objects I am using following in Update() calls,

transform.position = new Vector2 (transform.position.x, transform.position.y - (GameManager.Instance.currentGameSpeed * Time.deltaTime));

Also, I am surprised to see that game runs very smooth in iOS and in many android devices but some devices are behaving like jurks though they are having more than 1 GB ram and more resources than android devices in which game is working fine.

I am so tiered of looking for solution. Don't know what I am missing here.

Thank you in advance.