update에

$user = User::findOrFail($id);

$rules = [

'nickname' => '',

'email' => 'email|unique:users',

'password' => 'min:6|confirmed'

];

$this->validate($request, $rules);

if($request->has('name')) {

$user->name = $request->name;

}

if($request->has('nickname')) {

$user->nickname = $request->nickname;

}

if($request->has('email') && $user->email != $request->email) {

$user->email = $request->email;

}

if($request->has('password')) {

$user->password = bcrypt($request->password);

}

$user->save();

return response()->json(['data' => $user], 200);

여기서는 form-data보다는 x-www-form-urlencoded로 

여러가지로 테스트해보세요..