“I was doing fine until the microscope era began.”

This looks most like minor pest damage from something small feeding on the leaves or stems, such as mites, thrips, or a young scale/whitefly issue. The pale scarring and uneven leaf quality fit feeding injury better than a simple watering problem. Because the plant is otherwise upright and still green, this seems more like an early or mild pest issue than a major collapse. A secondary possibility is mild nutrient imbalance from weak fertilizing or uneven uptake in a container seedling, but that would usually cause more uniform yellowing rather than scattered scarring.