Thanks for the suggestions!
I've kept the humidity around 20-25% for the grow, but some of the dying leaves did feel squishy.
Not sure of my pH, didn't check it for the grow. Something to do next time though.
And possibly. What I forgot to mention was I was late on a watering, and as a result the one's leaves wilted dramatically. They seemed to perk up when I watered, but that's when the problems began. In any case, I harvested to avoid spreading to the buds.