Since Apotheosis 6.2.0 for Minecraft 1.19.2, a Withering Archer's signature withering cloud will persist for a bit under 2.8 hours after initial spawn, regardless of what happens to the Withering Archer itself.

Over time, in places where skeletons or their wither variant can spawn, this can create random 5-meter-wide spots which inflict withering on any entities entering them for the next in-game week, as if temporary, invisible, and long-range Wither Roses were placed at the last known locations of any withering archers which happened to spawn.

As far as I know, the default configuration of Apotheosis 8.2.1 for Minecraft 1.21.1 is still susceptible to this issue.

Would it be possible to expire Area Effect Clouds spawned as part of an Apothic Elite as soon as the Apothic Elite entity which spawned them is removed? This would resolve the issue completely.
Additionally, or as an easy workaround, the duration of the withering cloud can be reduced from 200000 to 24000 or less.