problem with loop and mesh values

Trying to delete n colored uvs and vertices from a mesh, but after 4 loops, it sais the index is out of range, even though it is counting down from top to bottom. i dont understand.

                     var vtxlist = new List.<Vector3>();     var vtx2 = mesh2.vertices;         vtxlist = vtx2.ToList();  
                     var nmlist = new List.<Vector3>();     var norms2 = mesh2.normals;  nmlist = norms2.ToList();  
                     var uvlist = new List.<Vector2>();      var uvv2 = mesh2.uv;                 uvlist = uvv2.ToList();  
                     var trilist = new List.<int>();                 var tris2 = mesh2.triangles;       trilist = tris2.ToList();  
                     print( trilist.Count + " yahhahyfuhsu  " + tris2.length);
                     
                     for (   var i = tris2.length-1;    i >= 0 ;    i --   )
                     {
                     if(uvv2[tris2[i]] == p0)
                         {
                         print(  " deleted mesh vales at index number " + i );

                         if (vtxlist[tris2[i]]  !=null)vtxlist.RemoveAt(tris2[i] );
                         if (nmlist[tris2[i]]  !=null)nmlist.RemoveAt(tris2[i] ); 
                         if (uvlist[tris2[i]]        !=null)uvlist.RemoveAt(tris2[i] );             
                         if (tris2[i]              !=null)trilist.RemoveAt(i );                              
                         }
                     }
                 mesh2.triangles = trilist.ToArray();
                 mesh2.normals = nmlist.ToArray();
                 mesh2.uv = uvlist.ToArray();
                 mesh2.vertices = vtxlist.ToArray();