If progress stops for a significant period of time, then you should use last-resort methods (i.e. a good clarifier or flocculant) since you may be down to chemicals or particles in the pool that are not filterable nor oxidizable by chlorine. It's not that common, but it does occasionally happen. As Casey noted, if you still have debris on the bottom, then that may continue to cloud/color the water so check that first.
When you used DE did you notice a pressure rise in the hours after using it (not just the small initial rise when adding it)? If not, then either you're not properly getting the water circulated or what is in the water is not filterable even by DE (which is unusual, though not unheard of).
I agree, it has been too long now, I should see a more significant positive result. As far as DE is concerned I did use DE. I did use it many times. I did see a pressure rise over time as you stated. I have been in the pool with the brush on the walls, bottom. I have checked and checked over and over for debris on the bottom by using vacuum to waste with a pool roller type vacuum and a brush style. I get almost no leaves or debris at any time when I vac.
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Oh, BTW you said "(i.e. a good clarifier or flocculant)". A good reccomendation would be nice..Thanks !