Where in Florida. I have lived in S. FL and currently live n N. FL. You said it is a salt pool, which SWCG do you have, and how well do you keep your pH regulated? High pH is the main factor that can cause calcium to precipitate out fo the water. If you are only testing your water once a month that is not enough to keep tabs on the pH in a salt pool. Also, how high is the TA of your water? Areas of Florida have water with very high TA.

I have never heard of "dead algae dust" , What exactly did it look like? To me it sounds like you have had problems with calcium precipitating out of solution. This really has nothing to do with TDS but everything to do with water balance (and most importantly pH since pH spikes are was tend to create the condition for this to happen. I would be very interested in seeing a full set of test results and knowing a bit more about what equipment you have (pump, filter, SWCG, etc.) and how often you test your water and make adjustments.