You need to make last named Ugweepai unkillable before his adds. If you kill him accidentally first, the last adds become immune, and need to evac, or reset the encounter, and be careful not to killed the named first after resetting it.
from test patch notes Karuupa Jungle: Heart of Conflict [All Versions] Ugweepai <Shaman of The Famine> will no longer take damage at the start of combat.