Did you steep grains and squeeze the bag? My first thought is tannins.
+1 on the green beer. Oktoberfest takes a while to age.
I don't know what the heck was going on with your airlock. I have some on batches that still have liquid after 6+ months. Is there a lot of temperature fluctuations in your house? You might want to start using vodka or Star San in your airlock if you're getting a lot of suck back.
Batch 1 Brewing
The American Revolution would never have happened with gun control.