Johny, are you using herx to mean "die-off" dead cooties getting stirred up?
"Bromism" (or bromide detox) has been used to describe Iodine displacing bromine from the fat tissues into the bloodstream, where it becomes bromide and causes a reaction just like taking bromide drugs.
Iodine chelates metals out too. But there isn't much reported that can be attributable to metal detox from iodine. Abraham says most Iodine chelated metals are excreted in the stool.
So, short answer, you may have several different things going on.