&*%*&#$&%*# phenolics - troubleshooting

I made a split batch of Hefeweizen (White Labs Hefe IV) with my neighbor. Fermented in 2 separate 6 gallon carboys. Kegged and bottled her half, tastes great. No offs that I can pick up. Finished a tick high at 1.016 instead of the 1.012 we were aiming for, but I can live with that. Put my half (also finished at 1.016) in a corney (tasted fine at that time) and put strawberries in it. Strawberries (frozen) were boiled and in a large hopsac to prevent as much of them from gooping up the beer as possible. Both kegs were cleaned at the same time using unscented oxyclean, vigorously rinsed, the sanitized with star san, dumped, pressurized, and the remaining san spray blown out. All water in our house is charcoal filtered so chlorine in any of the water shouldn't be a problem. Tasted the strawberry beer last night and damn it - I get a plastic taste. Doesn't make the beer undrinkable, but hell if I know where that came from.

So, all you brilliant brewers out there help me out because I'm going crazy on what could have caused that. I know the causes of undesirable phenolics and I feel like I've eliminated all of them from our brewing process. Fermenters were side by side, so temperature effect was the same on both Hefes. Beer is roughly 4 weeks old right now. Strawberries were boiled, put in the keg hot, and allowed to cool in the sealed keg before I racked the beer on top. Hopsac for the strawberries was sanitized in star san. Both used the same racking equipment. Do you think the strawberries could have reacted with the Hefe yeast to produce something that I'm identifying as plastic like? Has anyone used strawberries before and had this problem? Am I missing something basic?

Jason says I'm becoming paranoid and tasting an off in everything now (damn BJCP class). But it's driving me nuts.