I've had new-ish tanks get bacterial blooms after any substrate dust settled. Water changes made it worse (tried that years ago). Seems that the bacteria that naturally live in the tank can initially overpopulate, making the water cloudy, then they die off to a normal level.
In ecological popupation-dynamics terms, initial bacterial reproduction rates (r) cause the population to greatly exceed its carrying capacity (k). After this point, lack of resources causes r to drop, reducing the population (n). If n gets below k, r will increase (due to abundant resources), although r will be less than before since resources are not as overly abundant. Eventually, things settle out at k, and your water will be clear. It can take a couple of weeks. I would try to resist the temptation to change any water at this time, which would put you back toward the beginning. Been there, done that.
Wow. I must be feeling especially geeky today.
And, although I have used flocculants in the past for things, especially when I was feeling impatient, I am no longer a fan. A couple of weeks ago it killed my hand-collected swamp darters from a trip to Florida. I woke up in the morning, and they were all gone.