Back in September I made a beer with a packet of US-05, but the temperature got a little warm in my basement (around 74, so with fermentation, the wort might have been close to 80). I then pitched another beer onto this yeast cake and when that one was done, Next I made a 10gal batch and split the yeast cake between two fermenters.

After the first batch, the temps in my basement have lowered significantly and the beers have been fermenting in the lower 60s. I just got around to tapping the first beer which I fermented too high and it has a strong off flavor, I'd best describe it as a detergent taste. I attributed this flavor because of the high fermentation temperatures. I figured "time cures all", so I took this beer out of the kegerator and plan to let it age for a while. So I put the second beer on tap and it has a similar detergent taste despite fermenting in the mid to lower 60s.

So my question is, once the yeast is fermented at a high temperature, do the yeast mutate and should I not have used them in subsequent batches or could there be something else going wrong here?