Curled leaves

Leaf releasing moisture faster than it uptakes. Plant chooses which parts of leaf to "sacrifice" by choosing the least vital parts of a leaf to be cannabalized first. This is caused by a breakdown in water system and the cycle as a whole. Where the bottleneck is, could be a number of things. The plant actively manages balance primarily through stomatal control, to ensure that the rate of water uptake from the soil can keep pace with the rate of water loss to the atmosphere, thus preventing lethal levels of water stress. The entire system is a balance between the atmospheric "demand" for water and the physical limitations and resistances within the soil and the plant itself. Soil/Roots, Plant, Air/Atmosphere, I could waffle on forever, find where the bottleneck is and why water stopped moving.

Could be a few things... climate - temp/rh need to be considered together wind could do it Can't see much of the plant, but age - these don't look old enough for mottled leaves, though. Could be proximity of the medium messing with stomatas. It's not pH because it's only the older leaves and none of the new growth, which would be impacted by swinging pH. Can cross that off list. Even if it is from being shielded from light, there nothing to do about that. The leaves are still useful as they perform many tasks for the plant beyond absorbing light. Older shielded leaves won't stay as pretty as upper levels of canopy. I've got some twisted upside down but they still transpire. They still store nutrients. If it was a burden, the plant would shed it.