Unity Editor's Inspector Glitch while using OnGUI function

I don't know exactly how to explain it, so i'll post images to help

Whenever i try to create simple buttons, using OnGUI function (all codes are C#), somehow my editor have some kind of Glitch on the inspector, which make all itens become strangely deformed, as if they were buttons. It is weird, and it's driving me crazy, please help

Here my simple code:

 using UnityEngine;
 using System.Collections;
 
 public class ContainerControl : MonoBehaviour{
     public ParticleSystem particleReference;
     
     void OnGUI(){
         if(GUI.Button(new Rect(680,500,100,20),"Azul")){
             particleReference.startColor = new Color(0,0,0.5f,1);
             print("Azul");
         }
         
         if(GUI.Button(new Rect(680,530,100,20),"Vermelho")){
             particleReference.startColor = new Color(0.5f,0,0,1);
             print("Vermelho");
         }
         
         if(GUI.Button(new Rect(680,560,100,20),"Verde")){
             particleReference.startColor = new Color(0,0.5f,0,1);
             print("Verde");
         }
     }
 }

Normal:

Glitch: