The CYA levels tell the story.
CYA will hold the Cl until it is needed. At the level mentioned, the Cl will be used up rapidly, requiring lots of bleach to bring the Cl level back. The filter will then remove the "cloudy" stuff, giving you a "crystal clear" pool.
Bring the CYA level up to 50 ppm, keeping the other chemicals the same and see what happens.
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