Algae blooms can look white and cloudy with the tank lighting on in the
early stages. Look through the tank from the side with the tank light off.
If the water has a greenish tint, it's an algae bloom. The fresh water from
the water changes may be providing nutrients for the algae to thrive, along
with the decaying wastes from the period of infrequent maintanence. I
bought a diatom filter for problems like this.