S3 Fey Meander Spider Crab Boss Floor 180,Poison Stacks not being reduced with heal over time effect

[late leaf]

My Team was Fathomdown, Aspalta, Enna, Meggan and Torrin.
No stacks of poison was removed from Fathomdown on any heals and he seem to take increased frequency of stacks during the fight, making it completely impossible to kill the boss before stacks reach 100 and killing him.

S3 Fey Meander Spider Crab Boss Floor 180,Poison Stacks not being reduced with heal over time effect

[supple bane]

Your heroes get stacks when they hit the boss, and Fathom is very very multi-hit so it is only natural that he picks those stacks at crazy rate.