The reason why this is happening to you is because in Pokemon versions Diamond and Pearl, every two gym badges bumps the traded Pokemon obedience level up.
So here, from Bulbapedia, it says:
For every second Badge the maximum level of obeying Pokémon increases (2 Badges—level 30; 4 Badges—level 50; 6 Badges—level 70; 8 Badges—level 100).
Crasher Wake's badge (Fen Badge) will make your traded Pokemon listen up to level 50, as he is the fourth gym leader. However, you only have two badges, Gardenia's being the most recent you acquired. That means that traded Pokemon only up to level 30 will obey you.
Yes, you're next step should be to battle and defeat Maylene. Unfortunately, seeing as she's only the third Gym Leader, you're Pokemon will not listen to you unless they're level 30 or below.
Honestly, my advice is to either catch some Pokemon from the wild and start using them for the time being until you get badges that will make you respected enough by your traded Pokemon, OR, you can just keep on using those really strong but traded Pokemon in your team currently. It'll be incredibly frustrating since some times they won't listen, but it is your team after all.