Because your Piplup and Turtwig are Pokemon that were traded to you, they will not obey you because you don't have the required amount of badges that allows Pokemon in their level range to obey you. In most other Pokemon games, obtaining a specific badge will allow traded Pokemon up to a certain level to obey you. However, this is not the case in Diamond, Pearl, and Platinum. In D/P/Pt, the amount of badges you have determines what the maximum level traded Pokemon will obey you at is. To get your Piplup and Turtwig to obey you, you'll need to get the second badge, which will allow traded Pokemon up to level thirty to obey you.
TL;DR: Your Pokemon should start to obey you once you get a second badge, unless they are over level thirty.
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