I'd be inclined to say, wait on your WC . . . . are you topping off your tank daily (pretty much) with freshwater? There is no law that your tank is going to have all inhabitants die if you wait a few days for a water change until you get proper amounts of everything. In fact, I would say until you read up on risks of using tap or distilled water, to buy already mixed saltwater. It is not the answer or something to do long-term, but I would say you need to read the information and probably should have done so before adding inhabitants to the tank, but since there are get to reading asap.