I just fought a level 230 ish nemesis with a group that was mostly 170. This gave a significant amount of xp. It looks like when the creatures in the stable gain xp from combat it isn’t checking for max level each time the creatures level. I say this because some of my creatures that were near the max level for their (non existent) heredity gained too much xp and are now above their max level. Attached is a picture of one of my creatures above max level.
Found the problem, thanks!