Not all cloudiness is chemical participate. The effect could easily be a result of a bacterial bloom brought about by addition of the salt. In this well-written article about carbon-dosing, the observation of significant bacteria levels of Red Sea salt is briefly discussed.
"Bacterial Counts in Reef Aquarium Water: Baseline Values and Modulation by Carbon Dosing, Protein Skimming, and Granular Activated Carbon Filtration" By Ken S. Feldman, Allison A. Place, Sanjay Joshi, Gary White
http://www.advancedaquarist.com/2011/3/aafeature
"Five of the six salt mixes (Red Sea excepted) displayed little bacterial contamination beyond the pure water control, and the bacteria populations fluctuated but did not consistently rise over time as might be expected if sufficient nutrients were available (cf. Fig. 13). Thus, there is no reason to suspect that any of these five salt mixes themselves contribute to the high levels of bacteria in the make-up saltwater of Fig. 13. Red Sea salt, on the other hand, does appear to bring with it a not insignificant bacterial load. Once again, there was little increase over 5 days, indicating that sufficient nutrients for growth were not available under these "sterile" conditions.
What is so special about Red Sea salt? This salt, uniquely among the six mixes tested, is made, at least partially, by drying authentic seawater. Thus, it appears to retain some viable bacteria from the drying process. The other five salt mixes are prepared from mixing strictly chemical sources of the components. Overall, it appears justified to conclude that the significant populations of bacteria in mixed saltwater are a result of container contamination and not salt mix introduction per se."
Figure 15. Bacteria/mL count of six different brands of salt mix made up to 35 ppt salinity using RO/DI/0.2 uM filtered water in capped and foil-wrapped sterile flasks.
Being a partly "natural" product variation of effect should be expected. Some batches may produce greater "cloudiness", or none at all, than others based on oceanic conditions during collection of the raw materials going into the product. So a reasonable theory could be the elevated bacteria load brought in by this product is introduced to nutrients found in aquarium water which results in a large enough explosion of bacterial growth to temporarily cloud the tank. As shown in the article, bacteria can have a very rapid response time to various stimuli/factors. Is this THE cause, maybe, your observations fit the conclusion.
