Yup, I bet the STS is taking over and removing KH. KH is totally crashed and pH is at the bottom of the chart. Added 2 tablespoons baking soda; this ought to raise the KH by about 4 German degrees of hardness, and bring the pH up a bit.
I added a lot of rock as a background, stirring the substrate some. It clouded up while I was working, then settled down really fast. This is a very good substrate, that way. It has not even been an hour since I was up to my shoulders moving rocks around, and the water has only a slight haze remaining.