Chemical taste?

Just brewed byos December fat tire clone. Took preboil sample and it tasted sweet but fine. Forgot to take an og before pitching wyeast 1272 in nutrient pack, so I took one right after I pitched the yeast. Tasted this sample and got a strange chemical taste from it. Could this be from the whirlfloc I added or possibly the vitamins in the yeast pack? I didn't rinse the PBW from the fermenter with warm water but was thorough, then sanitized with star San. Could there still be residual PBW in the fermenter? I'm trying not to worry, but I'm perplexed! Any theories?

Hopefully you dechlorinated your brewing water prior to brewing. If not, the chlorinated compounds combine with phenolic compounds in the wort and beer to create chlorophenols which have a typically band-aid flavor and aroma.

I'm using the same water as I always do, and haven't had any problems before... Could something have changed that greatly in the grain bill to allow such flavors to be priduced? Also the Preboil/postmash sample tasted fine. Any thoughts?

I take it that you've never removed the chlorinated compounds before? If that's the case, you were just fortunate you didn't percieve them. Unfortunately, a drinker's perception becomes more acute after they have recognized the flavor. I suggest you include chlorine or chloramine removal into your brewing preparations and this malady will disappear. Either Campden tablets or activated carbon filtration will take care of this.

Nope haven't removed chlorine compounds before. I'll use rev osmosis water from here on out or campden tabs. Not worth the risk! Still just hoping this is a case of RDWHAHB. Thanks for your help!