Expedition Monsters Immune to everything?

Yeah as the title says but here's the catch. I didn't blow up remnants that make the monsters immune to physical damage (pure physical build) I've exploded the ones with immunity to cold damage and lightning damage but the monsters just decide that they are immune to everything. I've changed skills just to see if their HP bar will tick if I do fire damage etc and nothing happens. They are just immune and that is it.
Anyone else having that? Or, maybe someone can explain to me why that might happen? I'm looking for all kind of feedback
Thanks in advance

block, dodge, multiple reduced damage taken remnants.