2D Collider/Trigger on Canvas

The better way, to my way of to code, is to do checks on code, using SmoothDamp. So when pressure reach some value, it triggers an event on or off. So trigger do calls for animations on GUI element. I dont know to much about 2D Physics, so i cant help much ^^ desires to you good luck

So my workaround was to use 3D colliders instead and extend them over the Z axis in such way that the needle was unable to miss it, can't say if this was the best way to do this but it worked, yet I'm still curious as why the 2D collider didn't work in my UI.

Other question, do I need to make a script for each trigger? I made a script for each one of the triggers and attached it to it's respective game object like so:

    private void OnTriggerEnter(Collider needle)
 {
     if (needle.gameObject.tag == "Needle")
     {
         print("Max Pressure Reached"); 
         //Some more instructions related to the active trigger 9, 7, 5, 4, 0...           
     }
 }

and so forth with the other ones :( how can I put them all in a single script?