When Natsu, Wendy, Happy, and Carla went to Edolas, they couldn't use magic at first. Later, Natsu and Wendy were given the X-balls to regain their magic usage. Yet, even without the X-balls, Exceeds could use their magic. This is according to the wiki because they have their Magic located inside of their bodies just like the Mages of Earth Land.
Presumably, this is due to the fact that they are the only beings in Edolas whose Magic is located inside of their bodies, just like the Mages of Earth Land.
If both have their magic located within their bodies, then why are only the Exceeds able to use their magic, but Mages need those X-Balls?
Also related to this question, I was wondering why the Exceeds even lost their magic usage, to begin with. It was said that they need to have the right mindset to be able to use their magic, but when they entered Edolas for the first time, they didn't know magic was limited, so they were supposed to have the "right mindset" at that time right? So why did they lose their magic usage when they arrived?