I have a solid 3.5" wide kempas floor. It's on the first floor above a full, mostly-finished basement. The basement is always colder than the rest of the house. I run a dehumidifier in an unfinished portion (under my kitchen). The rest of the basement has a drop ceiling, with insulation between floors.

First floor tends to run around 35-50% humidity, but it is not specifically controlled.

I have slight cupping everywhere other than my kitchen. Have had it for about a year (2-year old floor). It seemed like it came and went the first year, then came and stayed the second. Do I have to dehumidify my whole basement? Any other ideas? Is my cupping "locked in?"

Thank you for posting your question.

It came and went the first year, and came to stay the second year.

Since we do not know the wood moisture content on top of the boards compared to the bottom of the boards and the difference between the wood flooring and the Sub-Floor, it would not be prudent to give a definitive answer.
However;; putting a de-humidifier in the basement to see the results cannot hurt anything. Certainly worth a try.