The jury is still out on Sr++. The issue is, is it really needed by corals or does it just act as a substitute ion for CA++. IMHO it is needed. The other issue is testing it. There are only two kits in this world both made by aquarium companies, so ask yourself that question........
I also agree with coral reef on the use of Sr-Chloride like Turbo Strontium
Here is something to read;
Strontium and the Reef Aquarium
Chemistry and the Aquarium
The issue on "iodine " is the same on kits. There is no need for it in a reef tank. If you were running a heavy Maco-Planted aquariumm it may be another issue. There is also the issue of crustacens, like shrimp, going into excessive molting==> dead. WC are enough Iodine