No, and unless your actually testing for iodine and finding low levels I would not dose any at all. It can be fatal and you won't know how much to dose if you aren't really watching it. Regular water changes should be enough to keep up with iodine in your tank.
And as far as not having to wory about your calclium with softies. I don't think it's nearly as important as it would be for an sps tank, but it's still an important aspect. Just because they don't grow a hard skelotan like an sps or
lps coral, they still use calcium for their sclerites.
Here is one of many articles you could find that touches on calcium in
soft corals.
http://www.reefkeeping.com/issues/2002-06/eb/index.php