There are many, many reasons why the water could turn cloudy, the sheer amount of Borax you've had to add to fix the pH problem being one of them....but another very common reason for cloudiness is impending algae bloom--have you consistently kept your Cl above 3 ppm, which is the absolute minimum for a CYA of 40? It's been awhile since you posted current testing numbers, if you would post a set of new ones, I'm sure we could help you figure it out.

Janet