I think you have two "maybes" here from me! The first is that I think that EKG hops do taste a bit "earthy" so that may be where you get the dirty taste from. That should improve a bit as the beer ages. Dry hopping with an ounce of them for a week might give you that flavor.
The second thought I had was that HSA probably isn't the issue, but maybe oxidation in either the transfer to secondary or to the bottle. My understanding, though, is that usually oxidation takes quite a while to give the "wet cardboard" flavor. Is it possible that you accidently aerated in one of the transfers, or when bottling?
It still could be just young beer, though. It definitely is still young, and at least the dirty flavor might get better in a couple of weeks.
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