5 weeks ago I brewed up a simple Belgian Blonde/Pale recipe to primary ferment with just white labs Brett B and Brett C split between the 10 gal batch into 2 different carboys. I have attached a couple of pictures to note a few differences that have already become very apparent.
The brew day recipe is as follows:
10 gal batch
18 lb 2-row
2 lb honey malt
OG - 1.061
IBU - 17 ( I forgot what hop I used) @60 min


Pic of the crazy hot break at the beginning of the boil. Other than this, there was nothing special about the brew day.

The first shock with this beer came roughly 4 weeks after brew day when I moved my fermenters from 65F fermentation chamber to a spare bed room to warm them up a bit to help reach terminal gravity.

The beers look drastically different. This was a split batch. I am still shocked at how big of a color change has taken place simply because of the yeast strain. The light carboy is pitched with Brett C and the dark carboy in the back was pitched with Brett B.

The final picture was taken last night.

To my surprise, a pellicle has begun to form on the Brett B beer. This tells me immediately that the white labs Brett B strain is not a pure strain. I suspected that the Brett C was not a pure strain of Brett but did not expect the B to be a mixed strain. The Brett C carboy hasn't formed any sort of pellicle yet, but did form a new krausen when put into the warmer (72F) bedroom.

Because of the color change and pellicle on the carboy that I thought I pitched Brett B into, I am currently assuming that I mixed up the starters. Brett C is typically used in flanders style beers, which typically undergo a color change during fermentation, and the white labs Brett C is suspected of not being a pure strain. I am going to monitor the lighter colored carboy over the next week to see if a pellicle forms on that beer as well. I have also already put an airlock on the dark carboy to hopefully restrict the amount of acid formed in the beer by removing the source of oxygen. I'd love to hear comments/suggestions or questions.