One mic is always quieter than the other

I use:

A ZEDI10 mized
Two Behringer C-3 mics
A laptop running Window 10

My problem:
No matter how I set the levels, one of the two mics always produces a track that is quieter than the other. Sounds like the speaker is standing far away no matter how close they get to the mic. The levels on the ZEDI show that both mics are equally hot, so I don’t think it’s the mic itself that’s causing the problem (although it might be.)

I have already tried:
Plugging in ONLY the suspect mic.
Switching the inputs (m1 to m2 etc.)
Setting the gain on the suspect mic higher than the other.

Conclusion:
Again, the meters show that the suspect mic is hot (when I turn up the gain it goes into the red.)
Not sure if Windows is causing the problem or if the mic is indeed faulty.

Thanks in advance for your help!