Trouble with Physics2D.OverlapArea detection

I'm trying to generate a grid and place floor blocks along the bottom row using the addBlock method, but the condition isn't working properly. It is supposed to detect if there are any objects in the area the new block will be placed in. The problem is, unless the gridBlockWidth and gridBlockHeight variables are less than .9, it detects objects and will only place every other block.

The draw lines show the area being looked at. Green lines is the area looked at if a block is placed and yellow is the area if a block cannot be placed.

Can anyone help me?

P.S. I'm also having trouble with the new blocks that are instantiated coming up as null when I try to change their scale size (the newBlock.transform.localeScale). If anyone can help with this as well, I'd be grateful.

 void createWorld()
         {
             gridWidth = Mathf.Clamp (gridWidth, 1, int.MaxValue); 
             gridHeight = Mathf.Clamp (gridHeight, 1, int.MaxValue); 
             levelGrid = new Vector2 [(gridWidth) * (gridHeight)]; 
     
             int i = 0;
             for (int col = 0; col < gridHeight; col++) 
             {
                 for (int row = 0; row < gridWidth; row++) 
                 {
                     levelGrid[i] = new Vector2(row + transform.position.x, col + transform.position.y); 
                     if (col == 0) //create a floor
                     {
                         //Debug.Log ("Adding " + floorBlock + " " + i);
                         addBlock (floorBlock, levelGrid[i]);
                     }
                     i++;
                 }
             }
         }
     
         //Adds a block to the grid unless a block already occupies the space
         public void addBlock(Object block, Vector2 vect)
         {
             float leftX = vect.x - gridBlockWidth / 2f + placementBuffer; 
             float botY = vect.y - gridBlockHeight / 2f + placementBuffer; 
             float rightX = vect.x + gridBlockWidth / 2f - placementBuffer; 
             float topY = vect.y + gridBlockHeight / 2f - placementBuffer;
             Vector3 bottomLeft = new Vector3 (leftX,botY,0f);
             Vector3 topRight = new Vector3 (rightX,topY,0f);
             Vector3 topLeft = new Vector3 (leftX,topY,0f);
             Vector3 bottomRight = new Vector3 (rightX,botY,0f);
             float timeForDebug = 60f;
     
             if (!Physics2D.OverlapArea (bottomLeft, topRight))
             {
                 //Debug.Log ("Instantiating at " + vect);
                 GameObject newBlock = Instantiate(block, new Vector3 (vect.x, vect.y, 0f), Quaternion.identity) as GameObject; 
                 //newBlock.transform.localScale = new Vector3(gridBlockWidth, gridBlockHeight, 0f); 

                 Debug.DrawLine(bottomLeft, bottomRight, Color.green, timeForDebug);
                 Debug.DrawLine(bottomLeft, topLeft, Color.green, timeForDebug);
                 Debug.DrawLine(topLeft, topRight, Color.green, timeForDebug);
                 Debug.DrawLine(bottomRight, topRight, Color.green, timeForDebug);
             }
             else //FOR DEBUGGING; this shows the area being looked at
             {
                 Debug.DrawLine(bottomLeft, bottomRight, Color.yellow, timeForDebug);
                 Debug.DrawLine(bottomLeft, topLeft, Color.yellow, timeForDebug);
                 Debug.DrawLine(topLeft, topRight, Color.yellow, timeForDebug);
                 Debug.DrawLine(bottomRight, topRight, Color.yellow, timeForDebug);
             }
         }