Bitterness - hop flavor taste perception

So I have a question in regards hop flavor - bitterness perception. I `ve brewed two different beers using different hops : 5 gals of a Kolsch and 5 gals of an IPL. The first one has been hopped only with Spalter hops and the latter with 4-5 different american hops.
The point is after I have kegged them and force carbed them I took a sample of both beers and they had a soft bright smooth bitterness and hoppy flavor.
They were in my fridge at 40 F for 1 month when I took them out and put them in my keezer to dispense.
Well, after 3-4 days of dispensing these beers I started to figure btterness and hop flavor have been increased, the soft bright smooth bitter-hoppy flavor has turned into a more hard -less pleasant taste, no off flavor, just too much intense erasing malt flavor, disbalancing the overall beer taste.I am a bit confused because aroma hops is still very pleasant as the one of the beginning but the flavor is too much harder than the one of the beginning.I do not suspect of oxidation cos i transfer from fermenter to keg using co2 to purge oxygen.No traces of any kind of infection either, I don`t know , maybe hops are too old ? I bought them in USA last june 16´. They are in their original bags brand YCHHOPS. Any thoughts?

 

OH man, how could I`ve been so blind !!!! You were right, the cuprit was a DIRTY tap ! .
My Goodness I `ve been dispensing these lovely beers through this dirty tap losing wonderful tastes, I think I always blame myself thinking my brews are crap, I need to give me a chance to feel more respectful!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!