How to modify a multidimensional array of objects and make it just an array of Laravel / PHP objects?

Hello everyone, this time I come to you for this problem that I have encountered and I have not been able to solve, I have the following code, which generates queries to various tables in my database, the names of the tables, I store them in a variable for later with a forEach loop generate the data as follows:

 public function getCustomData($id)
    {
        try {
            $tables = CatAdministrator::where('cat_modules_id', $id)->pluck('table_name');
            // Tables contiene ['tabla1','tabla2'];
            $data = null;
            foreach($tables as $table) {             
                $data .= DB::table($table)->get();
            }
     
            return response()->json([
                'success' => true,
                'data' => $data
            ]);
        }catch (\Exception $e) {
            return response()->json([
                'success' => false,
                'message' => $e->getMessage()
            ]);
        }
    }

The problem is that this generates the following structure in $data

$data = [
          {"id":1,"genero":"Masculino"},
          {"id":2,"genero":"Femenino"},
          {"id":3,"genero":"Indefinido"}
        ][
           {"id":1,"puestos":"Desarrollador Full Stack Developer"}
         ];

How can I remove the brackets from the second table so that I have a structure like the following?

$data = [
           {"id":1,"genero":"Masculino"},
           {"id":2,"genero":"Femenino"},
           {"id":3,"genero":"Indefinido"},
           {"id":1,"puestos":"Desarrollador Full Stack Developer"}
         ];

I thank you in advance for your answers and comments, and if anyone knows of a better way than mine to query multiple tables from an array with Laravel's QueryBuilder and return a better data structure, I'm open to receiving opinions. Without further ado, I thank you for your support.