there is no need for Iodine, at least not yet untill you reach Ultra low nutrition, in which case most of the times iodine is not needed [I was one of those who used to think iodine is what brings my blue SPS to life, but ever since I stopped, my blues are still blue. so I was wrong.]
K+ though, test it, and dose if needed. you dnt want to over dose this.
and of course, never use pottasium iodine to increase K+ concentration, you will kill corals due to iodine poisoning, if you tried to increase K+ with this.
HTH,