Could be a lot of things, meaning 3 evaporation is directly related to temperature and airflow, and indirectly related to relative humidity. I'd hang your devils lettuce out of the light, light degrades quality IMO. Rather than putting it in a jar, try putting it in a paper bag first, if it moistens up in a paper bag it's too wet to put in a jar, even though it feels crispy. I usually end up going back and forth from paper bag to jars, feebly trying to maintain the proper humidity. One of my old bosses grew catnip "AlaskaThunderStruck" they're whole attic was a drying room we set up to maintain 90f and 50%RH. I know catnip is not the same thing but drying herbs is drying herbs to some degree. to GK and Happy Growin'