With a swing arm hydrometer, make sure you tap the whole thing a couple of times to make sure there are no air bubbles stuck to the arm making it float artificially high. Also, try to rinse it with RODI
or distilled so no scale builds up on it which can impede the movement of the arm or weight it back down. Hydrometers are also sensitive to temperature. Two minutes should be enough for it to equalize itself, but it will read higher with cold water than with warm, all other things being equal.
As far as the water being cloudy after mixing, it sounds like the salt might not be getting completely dissolved. If you pour the somewhat mixed water into the tank, it will eventually dissolve, and that could be raising the sg
over time. Your mixing technique (28 hours with a powerhead) sound sufficient, unless there is a dead area in the mixing container where salt is settling. I mix mine with a powerhead in a five gallon bucket, and sometimes right under the powerhead I get some settling. I just move the powerhead around a couple of times to help get it stirred up. I am fortunate that I have my own RODI
at home, but this feeds from the cold line. This time of year (and into winter), it's much harder to get the salt dissolved than in summer and spring.
Sometimes you just get a not so good batch of salt. I seem to remeber reading earlier that you had some salt that was pretty clumpy? I suppose it's also possible that some of the salts in the mix kind of bonded to each other which could affect how wel they dissolve as well.