exactally like low tide.
gotta figure in the wild zoas can be exposed to direct sunlight for a couple hours.
thing with my buddy's polyps is after the iodine dip, that shiz was still all over the polyps.
the sunlight managed to dry that crap to a crisp, to the point that it just flaked off.
now, seein that white funk on your LPS is very scary. i would seriously consider a 100% wc (depending on your tank size)
id make a serious dip, and dip everything.
go to the chemistry forum too, see if you can attribute any of your problems to what those chemist dudes can come up with.
there is something bad in yer tank, maybe in the LR, deep in the sand bed, or somewhere else.
gotta figure what it is and how to get the hell rid of it...
good luck, you are in the right place for answers, ill tell ya whut...