Condensation on the outside of duct or leaky pipe?

I went to go turn on the water going to the outside of the house and noticed that were was what looked like condensation on the outside of the duct work near the unit. As far as I could tell, there weren't any visible leaks from pipes nearby but not 100%.

Here are some pictures (first 2 pictures are of outside, second 2 pictures of inside: http://imgur.com/a/TsCCa

Any ideas on what is happening? Is it condensation or am I just looking at a leaky pipe somewhere?

Thanks for your help!

submitted by /u/_johny
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