Some Wii drives are picky about media type and burn quality.
I've seen media work fine in one that won't detect in another, and then the same thing in reverse for another media.
Possibly the different burns on the same media are differing in their quality?
If that is all the different media you have then I would advise trying some more discs, particularly some +R media.

Are these discs all burned on the same burner? Can you try the same discs in another burner?
Is there a Wii C available to try the discs in?

Does the +RW Eledees work in Wii B? Just would be interesting to know more than helpful to you.

**EDIT**

OK now I feel dumb for missing this but... You do have the region free thing enabled for your WiiKey with the setup disc, don't you..?