the cloudy water was probably caused by adding the buffer which raised an already fine pH to a range that caused something to precipitate out of the water.
First we need to establish what you alk and pH are. Most people have a fine pH and alk just by doing regular water changes, so do a few water changes and then test. From there we can re-evaluate what you need to do. Its likely you dont need to do anything.
Also, when test the pH next time, test right before you turn the lights out on the tank. the pH will naturally rise during the day and will highest when the lights have been on the longest.