Yes your first three pokemon are fantastic. But the last three , especially cherrim needs to be changed. Train your ralts by competing it against those
NPCs at the main hall in reborn city as a Gardevoir will boost your team very much. Also if you have a dull key(i think found somewhere in the railnet) go to
the place where you fought Scraggy and Scrafty and you will see a door opened by that key. From there the Scraggy event will start .
Your donphan is good/ok so no serious need to replace that until you get further into the game.