Ideally it is best to let new SW mix overnight..for 2 purposes..one to allow the salt mix to completely dissolve (some brands dissolve much better than others) and secondly so the water gets oxygenated by the pump that is mixing the water (you want to distrub the surface of the water while it is mixing to allow oxygen in.)
I realize you were in a rush to do the water changes due to the iodine overdose, but unmelted salt crystals can do a lot of damage in a reef tank
I realize you were in a rush to do the water changes due to the iodine overdose, but unmelted salt crystals can do a lot of damage in a reef tank