I entered a homebrew competition recently with the 8th beer I have made and the judges found off-flavors of diacetyl, astringency, and slight warmth of aclohol in a low gravity, 1.040 OG, beer. This was a shock to me because I entered the second homebrew I ever made back in January in a homebrew competition and got 3rd place out of 8 people. I know my methods have only gotten better since then so I am having a hard time figuring out where these recent off-flavors are coming from. The two beers which had off-flavors were an extract Little Bear Session CDA and a partial mash RyePA.
I have been keeping notes of my beers and have not noticed the off-flavors until the beers have been bottled. Now that the off-flavor has been brought to my attention I do taste a slick or oily mouthfeel with my two most recent beers and a harsh astringent taste which I thought were the bittering hops. My thought is the issue could be from my bottling tubing, which came with my starter kit, because the tubing does have a light brown, sticky looking film on the inside; however, I do thouroughly sanitize everything with Star San. Could dirty tubing be the issue creating my off-flavors? If so, how long do people usually use their buckets, tubing, and other equipment before getting replacements?
Any advice is greatly appreciated!