Hi. Cloudy water, unless it's green water, is a bacterial bloom, as your tank is already established. As I understand it, you're getting cloudy water after doing a 25 - 50% water change.
The bacterial bloom is caused by an excess of food source, more than the bacteria can normally handle. Either the problem is already in the tank, or possibly if you're adding something to the new water when you do the changes that makes the water look cloudy. I guess it's probably the latter since you're doing frequent water changes.
I do 25% changes weekly, and it works for me. I would do something like that. I wonder if the pH thing is causing the cloudiness, and how long it lasts.