Did the Challenger hops seem fresh? Older or mishandled hops might not give you the punch you want. I learned that when you order hops, you really need to get them from a source that respects the hops... Yakima Chief Hops, Yakima Valley Hops, Hop Heaven, etc. I have been burned by "homebrew supply" hops more times than I care to say. Also, the way you store your hops matters. If you open a bag and put the remainder in the freezer, get a vac-sealer. I think the one I have was $30-something dollars on Amazon. Seal them back up and put them back in the freezer. This is especially true for hops you want to use for dry hopping. They need to be at (or close to) their peak if you want that character in the beer.