Not to my knowledge.Hardox is a low alloyed kind of steel getting most of the strength by mechanical means. Not chemical compounds or especialy toxic metals.
Maybe the coating on the hardox?

Did you also welded any zinc coated steel? As zinc fumes are known to cause flu like symptomes.

My college at work gets the same sympomes. Skin rash, easely burned, even fever just by welding with a part of his skin exposed. me on the other side, I do most of the small welding whout gloves. Only ali makes me cringe and grab every protection you can imagine.