Fermented Culture wrote:
I was going to say repitching yeast increases the esters from gyle to gyle then it starts to decrease again. For example John Kimmich explains that after a certain amount of repitches conan "hits a stride" (most likely more fruity esters).
However I don't know what the effect of doing starters in between repitching would do.
No way to tell apart from guessing. It could be that a yeast from your vessel, environment or even the wyeast packet has changed the profile. It could be fermentation, temperature, pitch rates, mixing etc. Was there much difference in lag time and fermentation profile? Does it taste like it has a hint of a previous brew? Did you pitch all of the starter?
BTW did you end up fixing that infection/bad brew from a while back?
Or, to add to the list, something like nutrient deficiency or too much/not enough oxygen.